josh-cs10_su11-20110801-1436.zip 2007101570 1.9.7+ (Build: 20091216) 2009111300 1.9.7 1312234588 http://sage.cs.berkeley.edu 3cf69de46e705aa0cd907131e30a906d internal

assignment true false 540 Card Sorting true false 541 Card Sorting Discussion true false 542 Card Sorting Discussion II true false 543 Card Sorting Discussion III true false 544 Card Sorting Discussion IV true false 545 Card Sorting Discussion V true false 546 Card Sorting Reflection true false 547 Submit-a-Species true false forum true false 1011 Describe a bug in the 'max' block true false 1012 Variable Names in Between true false 1013 Trash or Treasure? true false 1014 Comparing Algorithms true false 1015 Technology in Your Life true false 1016 Debrief true false label true false 2237 Welcome! Welcome to the UC-WISE module for CS... true false 2238 Learning GoalsGet comfortable with the Scratch use... true false 2239 User Interface Detective Work true false 2240 Broadcast true false 2241 Homework true false 2242 Optional Sections for Fun true false 2243 Learning Goals Learn to use key listene... true false 2244 Game controls true false 2245 Drawing true false 2246 Variables true false 2247 Homework true false 2248 Learning Goals Learn to use the if blo... true false 2249 Review: 'Change' versus 'Set' true false 2250 The If Block true false 2251 Random true false 2252 Number Guessing Game true false 2253 Rock, Paper, Scissors true false 2254 Homework true false 2255 Learning Goals Discover how to use the ... true false 2256 The Basics of BYOB true false 2257 Predicates true false 2258 Variables true false 2259 Functions make code easier to understand true false 2260 Homework true false 2261 Learning Goals Practice writing and rea... true false 2262 Introduction to Lists true false 2263 Lists and Sentences: The Index Variable Pattern true false 2264 Lists as Arguments true false 2265 Learning Goals Solidify understanding of wh... true false 2266 Learning Goals Get more practice with mak... true false 2267 More Practice With Lists: Game Board true false 2268 Sorting a List true false 2269 Drawing a Game Board true false 2270 Homework true false 2271 Introduction true false 2272 Timing Experiments true false 2273 TODO Make sure that you look at the concurrency ex... true false 2274 Learning GoalsIn Scratch / BYOB what a... true false 2275 Activities true false 2276 Background; fun sans-computer activities true false 2277 Scratch... you got some speed, man? true false 2278 Scratch... don't all talk at once! true false 2279 Scratch... some details to form a mental model true false 2280 Learning Goals Explore the idea of rep... true false 2281 Tree Recursion true false 2282 Fractals true false 2316 A Survey true false 2283 Linear Recursion true false 2284 Practice going from iteration to recursion and bac... true false 2285 Learning Goals Review the concept of r... true false 2286 Recursion Warm-up true false 2287 Applications of Recursion true false 2288 Learning Goals Comput... true false 2289 How Life Has Changed true false 2290 Example: Google true false 2291 Learning Goals Gain a... true false 2292 Real-world simulations true false 2293 Simulations in Scratch true false 2294 Background Reading true false 2295 Introducing the Problem true false 2296 The Computational Solution true false 2297 Debrief true false 2298 Tools Sprite true false 2299 Introduction true false 2300 Map true false 2301 Keep true false 2302 Combine true false 2303 Cascade true false 2304 Tic-Tac-Toe true false 2305 Learning Goals true false 2306 Digital devices, systems, and the networks tha... true false 2307 MapReduce Distributed Computing Pattern true false 2308 Let's start solving problems with MapReduce! true false 2309 Please complete the following two surveys before ... true false 2310 Extras! (A great place for new ideas!) true false 2311 Concurrency in the game of tag true false 2312 Trickiness true false 2313 Changing variables using block variables true false 2314 Changing variables by accessing a variable from wi... true false 2315 Colleen wants to add more stuff here, but needs to... true false quiz true false 826 Test Yourself: Go Bears! true false 827 Test Yourself: Different Ways to Broadcast true false 828 Homework: Survey true false 829 Test Yourself: Detecting a key press true false 830 Turns - test yourself true false 831 Repeat self-test true false 832 Which one goes faster? true false 833 Increasing the tempo true false 834 Non-numeric variables true false 835 Changing Variables true false 836 If: What would you expect? true false 837 Rock, Paper, Scissors: Choices true false 838 How was this made? true false 839 Don't use Script Variables Outside of their Script true false 840 Changing regular variables with block variables true false 841 Change a regular variable within a block true false 842 Quiz: Weird Cases true false 843 Quiz: Loops and Lists true false 844 Searching Through Time true false 845 Quiz true false 846 Different Trees Self Test true false 847 Different Versions of Tree true false 848 What was changed? true false 849 Where is the base case? true false 850 Tracing Code on Paper true false 851 Considering Exceptional Cases in the Range Function true false 852 Simulation today true false 853 Quick Review true false 854 Quick Review 2 true false 855 What kind of pattern was alpha? true false 856 What kind of pattern was Love? true false resource true false 3954 Welcome to Scratch true false 3955 Make a Sprite sing! true false 3956 Some Starting Scratch Lingo true false 3957 Experiment with a short Scratch play true false 3958 Single Step Mode true false 3959 Exporting Sprites true false 3960 Homework: Get Familiar with Scratch true false 3961 Optional: Musical Magic true false 3962 Optional: Electric Keyboard true false 3963 Moving with the Arrow Keys true false 3964 Two characters running! true false 3965 Game of TAG! true false 3966 Experiment with drawing commands true false 3967 Experiment with Repeat true false 3968 Tempo true false 3969 Change how fast the tempo changes true false 3970 Variable Tutorial (Scales) true false 3971 Common Bug - Set vs. Change true false 3972 Variable Sized Shapes true false 3973 Countdown true false 3974 Repeat Until true false 3975 Draw a Squiral true false 3976 Homework: Countdown with Sprites true false 3977 Homework: Draw a Picture in Scratch true false 3978 Homework: Survey #2 (due Friday) true false 3979 Reviewing Variables true false 3980 How many days are there in a given month? true false 3981 Random Character true false 3982 Number-Guessing Game v1.0 true false 3983 Number-Guessing Game v2.0 true false 3984 Rock, Paper, Scissors: Script true false 3985 Homework: Rock, Paper, Scissors true false 3986 Welcome to BYOB! true false 3987 Make a "Draw Shape" Block true false 3988 The Max Block true false 3989 Input types true false 3990 Composition of Functions true false 3991 Predicates true false 3992 Predicates: Make a "Between" block true false 3993 Difference between Arguments/Input and Variables true false 3994 Conflicts between regular variables and block variables true false 3995 Simplifying a tic-tac-toe board drawer using functions true false 3996 Homework: Brick Wall true false 3997 Make a List true false 3998 Read a List of Names true false 3999 Process a List true false 4000 Practice with Index Variables true false 4001 Remove List Elements true false 4002 Remove List Elements: Take Two true false 4003 Range of List Elements true false 4004 Processing a Sentence true false 4005 Swap List Values true false 4006 Check if a List is Sorted true false 4007 Check if a List is Sorted: Hint true false 4008 Everyone's Got Algorithms true false 4009 Teacher Resource: Searching & The Need for Speed true false 4010 Activity - Searching true false 4011 Activity - The Need for Speed true false 4012 The Need for Speed: Teacher Resource true false 4013 Algorithms in BYOB true false 4014 Improving Our Number Finder true false 4015 Too Many Blocks! true false 4016 Make a Game Board true false 4017 Get One Piece true false 4018 Error Checking true false 4019 Change a Piece Value true false 4020 Copy Letters: Hint true false 4021 Change a Piece Value: Take Two true false 4022 Sorting a List: Helper Functions true false 4023 Sorting a List true false 4024 Sorting a List: Implementation true false 4025 Optional: Sorting a Word true false 4026 Drawing the board (not the pieces) true false 4027 Homework, Part 1: Common Game Board Actions true false 4028 Homework, Part 2: Make a High-Score List true false 4029 A (Non-Video) Game true false 4030 Competing with Young Gauss true false 4031 Time is of the Es-sense true false 4032 Do You Have Time to Add? true false 4033 Constant-Time true false 4034 All the Numbers, All the Time true false 4035 Linear-Time true false 4036 Sum-thing's Up true false 4037 Constant versus Linear true false 4038 A Distinct Difference true false 4039 Quadratic-Time true false 4040 Logarithmic-Time true false 4041 View the lab true false 4042 Scratch Machine Concepts true false 4043 Scratch Play true false 4044 Scratch Debug true false 4045 Reflection true false 4046 Overview true false 4047 Scratch Modify true false 4048 Quiz Image true false 4049 Quiz Answer Explained true false 4050 Scratch Play true false 4051 Reflection true false 4052 Overview true false 4053 Scratch Play true false 4054 Reflection true false 4055 Recursive Tree Part 1 true false 4056 Recursive Tree Part 2 true false 4057 Vary your tree true false 4058 Random Tree true false 4059 Base Cases true false 4060 Snowflake true false 4061 C-Curve true false 4062 Google "Fractals in Nature" true false 4158 Make sure you have filled out the survey true false 4063 Write countdown using repeats/forever true false 4064 Countdown true false 4065 The Non-Recursive Countdown true false 4066 Tracing a Recursive Function true false 4067 Tracing a More Complicated Recursive Program true false 4068 Write a program that says numbers in a range true false 4069 Make a recursive squiral true false 4070 Example - Square each number true false 4071 Write a recursive block to add the digits in a number true false 4072 SOLUTION: recursive block to add the digits in a number true false 4073 Recursion in a Nutshell true false 4074 Practice: Aibohphobia true false 4075 Practice: Adding a range of numbers to a list true false 4076 Practice: Performing recursive operations on lists true false 4077 Flood fill true false 4078 A Prime Opportunity true false 4079 Apartment Hunting Throughout the Decades true false 4080 Life Before Search true false 4081 How Google Works true false 4082 Search Takes a Team true false 4083 Storing Data for Searching true false 4084 Practice: Working with Hash Tables true false 4085 Storing Complex Data true false 4086 Searching in BYOB true false 4087 Why we simulate true false 4088 Climate Change / Global Warming true false 4089 The Big Bang and the Beginning of the Universe true false 4090 The Formation of Life on Earth true false 4091 Collisions between Galaxies true false 4092 Space Shuttle / Jet / Car Design true false 4093 Medical Student Training true false 4094 Ecosystem Simulation true false 4095 Bioinformatics Background true false 4096 Background true false 4097 Overview true false 4098 Substring true false 4099 Overlap true false 4100 Shortest Common Superstring of 2 Strings true false 4101 The Snowball true false 4102 Congratulations true false 4103 How to load the Tools Sprite true false 4104 VIDEO true false 4105 "The Block" true false 4106 "Call" true false 4107 Higher Order Functions true false 4108 Introduction true false 4109 Using Map true false 4110 Transforming the Beatles true false 4111 Exaggerating your sentences true false 4112 Using Keep true false 4113 Count "ums" true false 4114 Choose Beatles true false 4115 Using Combine true false 4116 Calculate your GPA true false 4117 Letter Count true false 4118 Using Cascade true false 4119 Factorials true false 4120 Finding a Subword true false 4121 Important Note! true false 4122 Introduction true false 4123 Thinking about the Program Structure true false 4124 Triples true false 4125 Finding the Triples true false 4126 Finding the Triples (Cont') true false 4127 Can the Computer Win on this Move? true false 4128 Can the Computer Win on this Move? (Cont') true false 4129 Blocking the Opponent true false 4130 Best Free Square true false 4131 Finishing Up true false 4132 Final Comments and Optional Exercises true false 4133 View the Lab true false 4134 Overview true false 4135 Let's get started with MapReduce! true false 4136 Your first MapReduce : a simple sum-of-squares (we did it for you) true false 4137 Your second MapReduce : Alpha, the first word in the dictionary true false 4138 Your third MapReduce : Love, All the Beatles song titles with the word "love" in it true false 4139 Your fourth MapReduce : WordCount, a count of the number of times words appears true false 4140 Extra for Experts : the fifth MapReduce ... Google, building a Google-like index true false 4141 Quiz Answers true false 4142 Internal Course Survey true false 4143 AP Post-Course Survey true false 4144 Gregory true false 4145 Keep score in your game of tag true false 4146 Comparing two solutions to keep score true false 4147 TODO Roles of variables true false false course false true true true false false false instances

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22 7 2011 Summer BYOBisSNAP The Beauty and Joy of Computing CS10_su11

Professional Development for High School CS teachers

topics 1 3 Teacher Teachers Student Students 1 1309158000 30 2097152 0 0 0 0 USD 27 1 1 1266466122 1309973571 0 0 0 864000 1 0 0 0 3 Teacher editingteacher 14 0 1308898800 0 1308934751 3 manual 0 134 0 1308898800 0 1308934792 3 manual 0 161 0 1308898800 0 1308934902 3 manual 0 511 0 1308898800 0 1308934776 3 manual 0 535 0 1308898800 0 1308934702 3 manual 0 706 0 1308898800 0 1308934813 3 manual 0 2005 0 1309935600 0 1309975943 3 manual 0 5 Student student 514 0 1308985200 0 1309021050 514 manual 0 692 0 1309158000 0 1309236532 692 manual 0 694 0 1309935600 0 1310015355 694 manual 0 697 0 1308985200 0 1308991891 697 manual 0 1085 0 1308985200 0 1309057722 1085 manual 0 1596 0 1308985200 0 1309006409 1596 manual 0 1616 0 1310022000 0 1310052361 1616 manual 0 1803 0 1309935600 0 1309946559 1803 manual 0 1917 0 1309071600 0 1309156148 1917 manual 0 1960 0 1308985200 0 1308988614 1960 manual 0 1963 0 1308985200 0 1309007594 1963 manual 0 1964 0 1308985200 0 1309010266 1964 manual 0 1965 0 1308985200 0 1309010921 1965 manual 0 1966 0 1308985200 0 1309014551 1966 manual 0 1969 0 1308985200 0 1309030610 1969 manual 0 1970 0 1308985200 0 1309031749 1970 manual 0 1971 0 1308985200 0 1309046415 1971 manual 0 1972 0 1308985200 0 1309060410 1972 manual 0 1973 0 1308985200 0 1309061884 1973 manual 0 1974 0 1308985200 0 1309065792 1974 manual 0 1975 0 1309158000 0 1309209840 1975 manual 0 1976 0 1309158000 0 1309219455 1976 manual 0 1977 0 1309071600 0 1309102799 1977 manual 0 1978 0 1309071600 0 1309106333 1978 manual 0 1979 0 1309071600 0 1309110937 1979 manual 0 1984 0 1309158000 0 1309237165 1984 manual 0 1986 0 1309244400 0 1309318155 1986 manual 0 1987 0 1309244400 0 1309325928 1987 manual 0 1990 0 1309417200 0 1309435501 1990 manual 0 1992 0 1309503600 0 1309561725 1992 manual 0 2002 0 1309849200 0 1309913215 2002 manual 0 2003 0 1309935600 0 1309937122 2003 manual 0 2055 0 1310626800 0 1310695983 2055 manual 0

1331 admin 22 course-view r 0 1 Tjs= 1332 course_summary 22 course-view r 1 1 Tjs= 1333 participants 22 course-view r 2 1 Tjs= 1334 html 22 course-view r 3 1 Tzo4OiJzdGRDbGFzcyI6MTp7czo0OiJ0ZXh0IjtOO30= 1335 massaction 22 course-view r 4 1 Tjs=

626 0

<p><font size="5"><span style="font-family: verdana,arial,helvetica,sans-serif;"> <strong>CS10: The Beauty and Joy of Computing</strong></span></font></p> <p style="margin-left: 80px;"> <img border="0" width="303" vspace="0" hspace="0" height="222" src="$@FILEPHP@$$@SLASH@$nicetomeetyou.png" alt="'Hi! I'm Scratch.' 'I'm BYOB. Nice to meet you.'" title="'Hi! I'm Scratch.' 'I'm BYOB. Nice to meet you.'" /> </p>

1 8722 label 2237 1268105441 0 0 1 0 0 0 $@NULL@$

627 1

<span class="label"><font size="5">Broadcast, Animations, and Music! </font></span>

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628 2

<font size="5">Loops and Variables</font>

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629 3

<span class="label"><font size="5">Random, If and Input</font></span>

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630 4

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631 5

<font size="5">Lists I</font>

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632 6

<font size="5">Algorithms</font>

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633 7

<span class="label"><font size="5">Lists II</font></span>

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634 8

<font size="5">Algorithm Complexity</font>

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635 9

<font size="5">Concurrency</font>

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636 10

<span class="label"><font size="5">Recursion I</font></span>

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637 11

<span class="dimmed_text"><font size="5">Project Work</font> </span>

638 12

<span class="label"><font size="5">Recursion II</font></span>

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639 13

<span class="dimmed_text"><font size="5">Project Work</font></span>

640 14

<span class="label"><font size="5">Recursion III</font></span>

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641 15

<span class="label"><font size="5">Applications that Changed the World</font></span>

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642 16

<font size="5">Simulations (Sharks and Fish)</font>

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643 17

<span class="label"><font size="5">Simulations (Bioinformatics)</font></span>

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644 18

<span class="label"><font size="5">Lambda and HOFs I</font></span>

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645 19

<span class="label"><font size="5">Lambda and HOFs II</font></span>

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646 20

<span class="label"><font size="5">Distributed Computing</font> </span>

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647 21

<span class="dimmed_text"><font size="5">Project Brainstorming & Choosing Partners</font></span>

648 22

<span class="dimmed_text"><font size="5">Project Work</font></span>

649 23

<span class="dimmed_text"><font size="5">Project Work</font></span>

650 24

<span class="dimmed_text"><font size="5">Project Work</font></span>

651 25

<span class="dimmed_text"><font size="5">Project Work</font></span>

652 26

<span class="dimmed_text"><font size="5">Project Demos</font></span>

653 27

<font size="5">Final Surveys</font>

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654 28

655 29

<span class="dimmed_text"><font size="5">Text Processing/AI</font> </span>

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656 30

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14 manual 1 0 0 bh Brian Harvey bh@cs.berkeley.edu 0

Berkeley US en_utf8 99 1276548786 1307051503 1298513651 1307049485 192.54.222.11 1 0 2 1 0 1 0 1276548786 needed email_bounce_count 0 email_send_count 10 82 manual 1 0 0 clancy Michael Clancy clancy@eecs.berkeley.edu 0

Berkeley US en_utf8 99 1263941933 1308248580 1308079194 1308247972 128.32.45.163 Instructor, spring 2010 CS 61BL; director, UC-WISE project Web site (somewhat out of date) = http://www.cs.berkeley.edu/~clancy/web/index.html 1 0 2 1 0 1 0 1263942467 needed admin_bookmarks backups calendar_savedflt 15 email_bounce_count 1 email_send_count 1023 message_beepnewmessage 0 message_blocknoncontacts 0 message_emailaddress clancy@eecs.berkeley.edu message_emailformat 2 message_emailmessages 1 message_emailtimenosee 10 message_noframesjs 0 message_showmessagewindow 0 message_usehtmleditor 0 mod_forum_mod_form_showadvanced 1 134 email 1 0 0 headcrash Glenn Sugden headcrash@berkeley.edu 0 UC:Berkeley CS

Berkeley, CA.

Berkeley & Fairfax US en_utf8 99 1264037846 1312234158 1311956922 1312230832 136.152.36.152 http://www.aggroculture.com/ I've been a professional programmer (self-taught) in a previous life. I've decided to head to college to obtain a BS in CS and work towards teaching credentials. Have been programming ((more than) a handful of languages) for .. a long time. :) 1 0 1 1 1 0 0 1308075782 needed programming& hacking Programming& Hacking education Education ai (especially neural networking) AI (especially neural networking) making noise (industrial/experimental music) making noise (industrial/experimental music) ... ... blogpagesize 10 message_beepnewmessage 1 message_blocknoncontacts 0 message_emailaddress headcrash@berkeley.edu message_emailformat 1 message_emailmessages 1 message_emailtimenosee 10 message_noframesjs 0 message_showmessagewindow 1 message_usehtmleditor 1 mod_forum_mod_form_showadvanced 1 mod_label_mod_form_showadvanced 1 user_edit_form_showadvanced 1 161 email 1 0 0 advancedversion Jonathan Kotker jo_ko_berkeley@berkeley.edu 0

Berkeley US en_utf8 99 1264088667 1312061696 1310956427 1312061680 98.207.61.1 $@NULL@$ 1 0 2 1 1 1 0 0 needed blogpagesize 10 mod_resource_mod_form_showadvanced 1 511 email 1 0 0 luke.segars Luke Segars luke@lukesegars.com 0

Berkeley, CA US en_utf8 99 1275945931 1312145997 1312143073 1312145997 98.210.233.255 1 0 2 1 1 1 0 1307375159 needed blogpagesize 10 514 email 1 0 0 elemon Eugene Lemon elemon@pacbell.net 0

Oakland US en_utf8 99 1276120583 1311598108 1311155781 1311598029 196.215.129.59 Eugene Lemon in South Africa 1 0 2 1 1 1 0 1287378572 needed blogpagesize 10 535 email 1 0 0 ddgarcia Dan Garcia ddgarcia@cs.berkeley.edu 0

Berkeley US en_utf8 99 1276839758 1310388257 1309934514 1310380180 209.2.209.123 $@NULL@$ 1 0 2 1 1 1 0 0 needed blogpagesize 10 692 email 1 0 0 mclarkemiller Mary Clarke-Miller maryclarkemiller@gmail.com 0

Alameda US en_utf8 99 1277829820 1312075878 1312056620 1312058651 71.198.80.237 Irish born - first interested in computing age 13 - geeked out on programming magazines .. studied CS for "O" levels .. Went on to study Fine Art - but found the computer lab .. worked with Prof. Frazier using Geomod Ideas produced animation - was hired after graduation to study differential equations and how they might be used in yacht design .. Went on to work in Tv production computer graphics then onto Film - feature animation as 3D animator .. Assisted in pipeline set up for new animation company Phoenix AZ .. taught Traditional Artists to use digital tools .. worked with 2D and 3D software companies to iron out bug fixes and design interfaces ..Movies : Pebble and the Penguin, Anatasia, Bartok, Titian AE, Render TD on Power-rangers - asset management Fox interactive game - left industry to start animation, game and computer graphics programming degree at a Private College .. worked as associate Dean .. missed teaching - went to teach CTE programs at Elementary and High School .. just starting a Media Animation and Game design Academy and teaching one class at Berkeley City College .. 1 0 2 1 1 1 0 1309244271 needed love learning Love learning teaching teaching reading sci fi reading Sci Fi movies and raising my kids trish and brendan .. fo movies and raising my kids Trish and Brendan .. Fo blogpagesize 10 694 email 1 0 0 smorris Sean Morris sean.smorris@gmail.com 0

Berkeley US en_utf8 99 1277829766 1312199245 1311995183 1312196183 99.2.150.194 $@NULL@$ 1 0 2 1 1 1 0 0 needed 697 email 1 0 0 onyeador Emmanuel Onyeador onyeador@ousd.k12.ca.us 0

Oakland US en_utf8 99 1277830365 1312218516 1311538775 1312218383 64.73.240.139 $@NULL@$ 1 0 2 1 1 1 0 0 needed 706 email 1 0 0 navin.eluthesen Navin Eluthesen navin.eluthesen@berkeley.edu 0

Berkeley US en_utf8 99 1278353017 1312166995 1310952445 1312165306 24.6.6.232 $@NULL@$ 1 0 2 1 1 1 0 0 needed 1085 email 1 0 0 jnoko Judy Okolie history30@yahoo.com 0

Oakland US en_utf8 99 1291487551 1310656840 1309070479 1310651971 78.116.13.131 I teach Multimedia and Computer Applications at Tennyson High School in Hayward. 1 0 2 1 1 1 0 1309065012 needed blogpagesize 10 1596 email 1 0 0 bfranke Baker Franke baker.franke@gmail.com 0

Chicago US en_utf8 99 1298645355 1311963250 1310129623 1311961111 98.212.43.108 http://bakerfranke.com My name is Baker Franke. Yes Franke (pronounced: "Fran-kee") is my last name, and Baker is my first name. I promise I'm not mixing this up. Baker is my mother's maiden name, so now you know.<br /><br />I teach computer science in the high school at the <a href="http://ucls.uchicago.edu">University of Chicago Laboratory Schools.</a> It's a private K-12 school with about 1700 total students, situated on one city block on the University of Chicago campus. The "schools" are the lower school, middle school, and high school. Though we are one large institution now, the word "schools" alludes to significant periods of the school's history, even back to when the school was in its embryonic stages as John Dewey's educational Laboratory, in which there really were completely different schools (with different administrations) operating within the same building. It really was a laboratory. The high school is now referred to as "U-High" and we share an (unfortunate) mascot with the University...the "Maroons."<br /><br />I've been teaching Computer Science for ten years (seven of them at U-High). I'm the vice-president of our local CSTA chapter and one of the two CSTA Leadership Cohort members for Illinois (Don Yanek, also taking this course, is the President and the other cohort member).<br /><br />If I'm not teaching I'd rather be riding my bike or working with wood. For cycling, I usually train in order to go on some 7-10 cycling trip in some place that has hills or mountains (the 47th street overpass is the biggest hill in Chicago). This year I'm going to Colorado to follow a professional stage race happening around the state. I'm hoping to climb 20,000+ feet over the course of the week.<br /><br />I like to build things out of wood, too. I started as a rough carpenter, but recently have gotten into the finer craftsman-like things - fancy joinery mostly. I got a table saw for Christmas so I have to use it, right? Ask me about why woodworking makes me a better programmer.<br /><br />Also, I coach the girls basketball team at U-High. Basketball in Chicago is kind of a big deal - it's like football in Texas - so I forget how much of my time and energy this takes up. It's fun though. Talk to me about the similarities between basketball and computer science sometime.<br /> 1 0 2 1 1 1 0 1309023821 needed cycling basketball woodworking Cycling Basketball Woodworking user_edit_form_showadvanced 1 1616 email 1 0 0 sageparade Sage Moore sageparade@gmail.com 0

Oakland US en_utf8 99 1299296643 1310151432 1310142764 1310143733 41.140.146.220 $@NULL@$ 1 0 2 1 1 1 0 0 needed 1803 email 1 0 0 msdeebee Stephanie Darrough-Butler msbutler2@gmail.com 0

San Leandro US en_utf8 99 1308531054 1310386002 1310141101 1310369246 71.198.76.63 $@NULL@$ 1 0 2 1 1 1 0 0 needed blogpagesize 10 1917 email 1 0 0 kameny Susie Kameny susie@susie.com 0

San Francisco US en_utf8 99 1308614923 1309207504 1309156047 1309206942 66.245.217.85 I am currently an elementary teacher for SFUSD. 1 0 2 1 1 1 0 1309157702 needed art art cooking Cooking traveling Traveling blogpagesize 10 1960 email 1 0 0 test3 Test3 Student natesmail6@uclink.berkeley.edu 0

ldssdf UZ en_utf8 99 1308988405 1308988990 0 1308988442 71.139.180.148 $@NULL@$ 1 0 2 1 1 1 0 0 needed 1963 email 1 0 0 nmattix Nathan Mattix nmattix@piedmont.k12.ca.us 0

Livermore US en_utf8 99 1309007453 1311705974 1311702690 1311705764 99.40.55.118 $@NULL@$ 1 0 2 1 1 1 0 0 needed 1964 email 1 0 0 nmann Natalie Mann nmann@ousd.k12.ca.us 0

Richmond US en_utf8 99 1309010213 1309996153 1309804817 1309996153 108.78.248.115 $@NULL@$ 1 0 2 1 1 1 0 0 needed blogpagesize 10 1965 email 1 0 0 dyanek Don Yanek dgyanek@cps.edu 0

Chicago US en_utf8 99 1309010866 1311103033 1310648066 1311103032 71.194.134.31 I teach CS at Northside College Prep HS in Chicago. Northside is a public, select enrollment magnet school. I have been teaching for 22 years [CS for 16]. I currently teach CS1: Java and Media Computation, CS3: Advanced Data Structures, and Exploring Computer Science [1st time this fall]. I am also the president of the Chicago Chapter of the CSTA and a state representative to the CSTA Leadership Cohort. 1 0 2 1 1 1 0 1309011965 needed i am a avid music listener and collector. i have a I am a avid music listener and collector. I have a cds CDs and digital recordings. i also enjoy cooking. howe and digital recordings. I also enjoy cooking. Howe most of my time is spent is with my wife most of my time is spent is with my wife susan Susan wrangling our three young boys: oscar [10] wrangling our three young boys: Oscar [10] simon [6] Simon [6] and evan [6]. and Evan [6]. user_edit_form_showadvanced 1 1966 email 1 0 0 gbotha101 Glen Botha gbotha@gmail.com 0

San Francisco US en_utf8 99 1309014507 1311897595 1311090299 1311897594 75.36.151.172 I am a teacher at June Jordan School for Equity in San Francisco. 1 0 2 1 1 1 0 1309014662 needed user_edit_form_showadvanced 1 1969 email 1 0 0 mdeister Myra Deister mjdeister@fjuhsd.net 0

Fullerton US en_utf8 99 1309030540 1312172257 1312151239 1312165372 99.177.190.199 $@NULL@$ 1 0 2 1 1 1 0 0 needed blogpagesize 10 1970 email 1 0 0 castle.jeff@gmail.com Jeff Castle jcastle@ausdk12.org 0

San Francisco US en_utf8 99 1309031687 1311779379 1311610564 1311777444 174.28.246.188 I teach computer science, graphic design and film production at Albany High School in the San Francisco Bay Area. I have a masters degree in education, a California single-subject credential, and a CTE credential in media, arts and entertainment. I have over ten years of teaching experience in both formal and informal education, including K-12 classrooms, science museums and the private sector. My non-teaching experience includes driving double-decker buses and working in a beer brewery. Dog lover. Foodie. 1 0 2 1 1 1 0 1309032088 needed 1971 email 1 0 0 barbaralind Barbara Lind barbara_lind@sbcglobal.net 0

oakland US en_utf8 99 1309046185 1310941576 1310410947 1310941575 69.232.201.33 <font size="3"><span style="font-family: impact;"> Barbara Lind's Profile </span></font> 1 0 2 1 1 1 0 1309130024 needed music music drawing drawing exercising exercising cooking and eating with friends and family cooking and eating with friends and family and learning byob this summer and learning BYOB this summer 1972 email 1 0 0 cthiel Chris Thiel cthiel@sfhs.net 0

La Canada US en_utf8 99 1309060332 1311970006 1311869209 1311962008 67.203.132.210 Mathematics, AP Comp Sci and AP Statistics teacher at St Francis High School in La Canada, CA 1 0 2 1 1 1 0 1309670831 needed 1973 email 1 0 0 orhsgolf Tony Diaz adiaz@eduhsd.net 0

El Dorado Hills US en_utf8 99 1309061816 1311545107 1311472783 1311545107 24.7.140.36 <p>Born in Saipan (Northern Mariana Islands), grew up in Gresham, OR. Graduated from Willamette University in Salem, OR, with a mathematics degree and masters in teaching. Taught high school mathematics for 15 years in Eugene, OR, Roseville, CA, and currently in El Dorado Hills, CA. Married 16 years and have 3 wonderful children.</p> 1 0 2 1 1 1 0 1309062729 needed cooking (that's my clam chowder @ local restaurant Cooking (that's my clam chowder @ local restaurant spending time with my family spending time with my family hiking/outdoor activities hiking/outdoor activities road trips road trips and learning new things! and learning new things! 1974 email 1 0 0 trentkay Trent Kay Maverick trentkay@stanford.edu 0

Stanford US en_utf8 99 1309065735 1312187337 1310226058 1312177273 173.166.233.97 I teach 6th and 7th grade CS (as well as 7th grade math!) at The Girls' Middle School in Mountain View, CA. I'm a graduate of Stanford's Teacher Education Program (STEP), and I'm certificated to teach mathematics. I got my B.A. in linguistics at a tiny hippie school in the Berkshire mountains (that's rural western Massachusetts), where I studied five languages (ASL, Hawaiian, Hebrew, Japanese and Latin) and wrote a young adult novel for my bachelor's thesis. Growing up I planned to work in the book publishing industry, and even interned with Random House and The MIT Press. In grad school I became an indie rock / college radio disc jockey, and was the Music Director at KZSU (Stanford's campus station) from 2009 to 2011. My current interests seem to be learning Japanese, eating pho, reading "those books I should have read in college", and getting girls into engineering.<br /> 1 0 2 1 1 1 0 1309072563 needed indie rock indie rock japanese Japanese young adult fiction young adult fiction agricola Agricola mixtapes mixtapes pho pho classic math problems classic math problems 1975 email 1 0 0 miltfriedman Milt Friedman milt-friedman@att.net 0

Alameda US en_utf8 99 1309072183 1312061178 1312009705 1312061178 68.121.163.1 I am a facilitator (teacher to you) at Alameda Community Learning Center. I have used Scratch in our 6th grade exploration class, along with basic construction projects. We have always had a strong learn by doing philosophy. I like learning about computing! 1 0 2 1 1 1 0 1309075427 needed 1976 email 1 0 0 tinachowgarcia tina garcia ritaannaliciagarcia@gmail.com 0

Oakland US en_utf8 99 1309100611 1309633624 1309219584 1309633624 208.54.5.157 $@NULL@$ 1 0 2 1 1 1 0 0 needed 1977 email 1 0 0 sallen Stephanie Allen sallen@eduhsd.net 0

El Dorado Hills US en_utf8 99 1309102726 1312061324 1311780325 1312059719 108.76.188.241 I graduated in 1987 with a computer science degree from CSU Sacramento and worked in the industry until 2003 when I decided to stay home with my small children. I started substituting at their schools, got my teaching credential and am now teaching math and AP Computer Science at Oak Ridge High School. I have been teaching for four years. 1 0 2 1 1 1 0 1309103814 needed bike riding Bike riding yoga yoga music music having fun with my family. having fun with my family. 1978 email 1 0 0 skendall Susan Kendall susan.kendall@santacatalina.org 0

Pebble Beach US en_utf8 99 1309105997 1309123660 0 1309115432 67.188.72.245 $@NULL@$ 1 0 2 1 1 1 0 0 needed blogpagesize 10 1979 email 1 0 0 p1clifford80 Tom Clifford acarmelrunner@gmail.com 0

Carmel US en_utf8 99 1309110772 1312048227 1310951077 1312047120 76.215.158.66 Hello 1 0 2 1 1 1 0 1309128817 needed 1984 email 1 0 0 pkelly42 Philip Kelly philip@chatch.es 0

Berkeley US en_utf8 99 1309237086 1312167012 1311979946 1312166263 67.188.222.172 Currently a freelance web developer but will be applying for credential programs in the Fall. My career into education begins! 1 0 2 1 1 1 0 1309242766 needed programming Programming backpacking backpacking rock climbing Rock Climbing 1986 email 1 0 0 mcoler Malinda Coler malinda.coler@gmail.com 0

Mountain View US en_utf8 99 1309318020 1310505326 1310425684 1310504798 76.102.52.88 I'm a teacher at a non public school in San Jose and am enrolling in this course in order to develop an introductory CS class. 1 0 2 1 1 1 0 1309318357 needed learning learning foreign languages Foreign Languages literature literature travel travel teaching teaching writing writing cooking Cooking blogpagesize 10 1987 email 1 0 0 benchun Ben Chun benchun@gmail.com 0

San Francisco US en_utf8 99 1309325887 1309326071 0 0 208.90.212.18 http://galileoweb.org/chunb MIT class of 2000 (Course 6), Macromedia, Exploratorium, Adobe, Leadership Public Schools Richmond, Galileo Academy of Science & Technology, Middle East Education Through Technology, Google 1 0 2 1 1 1 0 1309326071 needed user_edit_form_showadvanced 1 1990 email 1 0 0 bauerm@iit.edu Matthew Bauer bauerm@iit.edu 0

Chicago US en_utf8 99 1309435371 1310599663 1310565131 1310596551 68.251.46.10 I teach computer science at Illinois Institute of Technology 1 0 2 1 1 1 0 1309435686 needed 1992 email 1 0 0 andrewcarlos Andrew Carlos andrewcarlos@gmail.com 0

Santa Clara US en_utf8 99 1309561692 1311271383 1311262799 1311271383 24.104.131.50 $@NULL@$ 1 0 2 1 1 1 0 0 needed 2002 email 1 0 0 sean.smorris Sean Morris smorris@ausdk12.org 0

Berkeley US en_utf8 99 1309913151 1309913216 0 0 99.35.216.198 $@NULL@$ 1 0 2 1 1 1 0 0 needed 2003 email 1 0 0 maafigueye Maafi Gueye maafi.gueye@neaclc.org 0

Alameda US en_utf8 99 1309937004 1311958712 1311124077 1311957032 75.52.121.106 Lead Facilitator at Nea Community Learning Center, Alameda's first K-12 charter school. 1 0 2 1 1 1 0 1309938592 needed african dance and music African dance and music canoeing canoeing camping camping gardening gardening all things art all things art dogs and kids dogs and kids blogpagesize 10 2005 email 1 0 0 kchaynie Kathleen Haynie kchaynie@stanfordalumni.org 0

Skillman US en_utf8 99 1309973760 1309973841 0 0 68.45.167.60 $@NULL@$ 1 0 2 1 1 1 0 0 needed 2055 email 1 0 0 pstclair Pat St. Clair pstclairap@gmail.com 0

Edmond US en_utf8 99 1310695957 1311963605 1311960811 1311963541 72.198.21.97 $@NULL@$ 1 0 2 1 1 1 0 0 needed blogpagesize 10 5 Survey system pactFakeStamp1263859879711925496 0 999 6 Pre system pactFakeStamp1263859879712338524 5 999 82 0 What year are you? What year are you? 1 0 0 multichoice 1 pactFakeStamp1263859879712142740 pactFakeStamp1263859879712515888 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 0 149,150,151,152,153 1 0 123 149 1st 1 150 2nd 0 151 3rd 0 152 4th 0 153 5th or greater 0 83 0 Have you declared your major? Have you declared your major? 1 0 0 multichoice 1 pactFakeStamp1263859879712753514 pactFakeStamp1263859879712728146 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 0 154,155 1 0 123 154 Yes 1 155 No 0 84 0 What is your current or intended major? What is your current or intended major? 1 0 0 essay 1 pactFakeStamp1263859879712506517 pactFakeStamp1263859879712556175 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 156 0 85 0 How many units do you plan to take this semester? How many units do you plan to take this semester? 1 0 0 multichoice 1 pactFakeStamp1263859879712364899 pactFakeStamp1263859879712386388 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 0 157,158,159,160,161,162,163,164,165 1 0 123 157 less than 12 1 158 12 0 159 13 0 160 14 0 161 15 0 162 16 0 163 17 0 164 18 0 165 19 or more 0 86 0 Are you enrolled for (or attending more classes than you plan to take this semester? Are you enrolled for (or attending more classes than you plan to take this semester? 1 0 0 multichoice 1 pactFakeStamp1263859879713384660 pactFakeStamp1263859879713712858 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 0 166,167 1 0 123 166 Yes 1 167 No 0 87 0 Are you friends with anyone in the class? Are you friends with anyone in the class? 1 0 0 multichoice 1 pactFakeStamp1263859879713227129 pactFakeStamp1263859879713598312 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 0 168,169 1 0 123 168 Yes 1 169 No 0 88 0 Are you friends with anyone who has taken this or a related course? Are you friends with anyone who has taken this or a related course? 1 0 0 multichoice 1 pactFakeStamp1263859879713151826 pactFakeStamp1263859879713204799 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 0 170,171 1 0 123 170 Yes 1 171 No 0 89 0 Do you consider yourself a math person? Do you consider yourself a math person? 1 0 0 multichoice 1 pactFakeStamp1263859879713274830 pactFakeStamp1263859879713249650 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 0 172,173 1 0 123 172 Yes 1 173 No 0 90 0 Have you programmed before? Have you programmed before? 1 0 0 multichoice 1 pactFakeStamp1263859879713844501 pactFakeStamp1263859879713522223 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 0 174,175 1 0 123 174 Yes 1 175 No 0 91 0 I will definitely take this course I will definitely take this course 1 0 0 multichoice 1 pactFakeStamp126385987971386624 pactFakeStamp1263859879715306503 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 0 176,177,178,179 1 0 123 176 Agree 1 177 Agree somewhat 0 178 Disagree somewhat 0 179 Disagree 0 92 0 I am more prepared than other students in the class I am more prepared than other students in the class 1 0 0 multichoice 1 pactFakeStamp1263859879715251228 pactFakeStamp126385987971554334 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 0 180,181,182,183 1 0 123 180 Agree 1 181 Agree somewhat 0 182 Disagree somewhat 0 183 Disagree 0 93 0 This course will be fun This course will be fun 1 0 0 multichoice 1 pactFakeStamp1263859879715190124 pactFakeStamp1263859879715819837 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 0 184,185,186,187 1 0 123 184 Agree 1 185 Agree somewhat 0 186 Disagree somewhat 0 187 Disagree 0 94 0 I can do well in this course I can do well in this course 1 0 0 multichoice 1 pactFakeStamp1263859879715585456 pactFakeStamp1263859879715439019 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 0 188,189,190,191 1 0 123 188 Agree 1 189 Agree somewhat 0 190 Disagree somewhat 0 191 Disagree 0 95 0 This course will be harder than other courses This course will be harder than other courses 1 0 0 multichoice 1 pactFakeStamp1263859879716703123 pactFakeStamp1263859879716876930 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 0 192,193,194,195 1 0 123 192 Agree 1 193 Agree somewhat 0 194 Disagree somewhat 0 195 Disagree 0 96 0 Why are you interested in taking this course? Why are you interested in taking this course? 1 0 0 essay 1 pactFakeStamp1263859879716769878 pactFakeStamp1263859879716490859 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 196 0 97 0 Please list any reasons why you might not take this course Please list any reasons why you might not take this course 1 0 0 essay 1 pactFakeStamp1263859879716168422 pactFakeStamp1263859879716610384 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 197 0 98 0 sex: sex: 1 0 0 multichoice 1 pactFakeStamp1263859879716151104 sage.cs.berkeley.edu+100827182819+HBgLZJ 0 1234567890 1282933699 $@NULL@$ 5 0 198,199,4202 1 0 123 198 Male 1 199 Female 1 4202 Decline to state 1 99 0 Ethnicity Ethnicity 1 0 0 multichoice 1 pactFakeStamp1263859879716620421 sage.cs.berkeley.edu+100827182839+XWn09a 0 1234567890 1282933719 $@NULL@$ 5 0 200,201,202,203,204,205,206,207,208,209,210,211,4203 1 0 123 200 American Indian/Alaska Native 1 201 Chinese/Chinese-American 0 202 East Indian/Pakistani 0 203 Japanese/Japanese-American 0 204 Korean/Korean-American 0 205 Filipino/Filipino-American 0 206 Pacific Islander 0 207 Other Asian 0 208 African-American/Black 0 209 Mexican/Mexican-American/Chicano 0 210 Other Spanish-American/Latino 0 211 White/Caucasian 0 4203 Decline to state 0 100 0 If you would be willing to be contacted for an interview please provide your email address below. We're going to try to pay people about $5 for a 30 minute interview. If you would be willing to be contacted for an interview please provide your email address below. We're going to try to pay people about $5 for a 30 minute interview. 1 0 0 essay 1 pactFakeStamp1263859879717284872 pactFakeStamp1263859879717572040 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 212 0 736 Default for The Beauty and Joy of Computing The default category for questions shared in context 'The Beauty and Joy of Computing'. course sage.cs.berkeley.edu+100218042912+YBkdPq 0 999 3186 0 New Star Pattern What would you need to fill in the blank below with to draw the picture shown on the right? <br /> <div style="margin-left: 120px;"><img hspace="0" height="122" border="0" width="166" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab01$@SLASH@$FillInStar.jpg" alt="Fill In the Blanks" title="Fill In the Blanks" /><img hspace="0" height="181" border="0" width="209" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab01$@SLASH@$FunnyStar.jpg" alt="Funny Star" title="Funny Star" /></div><br /> 1 0 0.1 shortanswer 1 sage.cs.berkeley.edu+100218054556+F97qEs sage.cs.berkeley.edu+100218054816+KPzLEt 0 1266471956 1266472096 5 5 8523,8524 0 8523 9 1 8524 * 0 Nope! Try again! 3187 0 Total Turns How far did the character turn in total when it drew the square? 1 1 0.1 numerical 1 sage.cs.berkeley.edu+100715045202+4bC1QQ sage.cs.berkeley.edu+100715045203+VG3hZW 0 1279169522 1279169522 5 5 8525 8526 8525 360 1 8526 * 0 3188 0 Total Turns Triangle How far did the character turn in total when it drew the triangle? 1 1 0.1 numerical 1 sage.cs.berkeley.edu+100715045221+S0d7NJ sage.cs.berkeley.edu+100715045221+r5ZqzZ 0 1279169541 1279169541 5 5 8527 8528 8527 360 1 8528 * 0 3189 0 Total Turns Pentagon How far did the character turn in total when it drew the pentagon? 1 1 0.1 numerical 1 sage.cs.berkeley.edu+100715045339+RMaHYF sage.cs.berkeley.edu+100715045351+rgOVo1 0 1279169619 1279169631 5 5 8529 8530 8529 360 1 8530 * 0 3190 0 Total Turns Hexagon Next you're going to draw a hexagon, how far will the character turn in total when it draws the hexagon? 1 1 0.1 numerical 1 sage.cs.berkeley.edu+100715050512+Jw94vs sage.cs.berkeley.edu+100715050633+ciTqjW 0 1279170312 1279170393 5 5 8531 8532 8531 360 1 8532 * 0 3191 0 Total Turns Circle Next you're going to draw a circle, how far will the character turn in total when it draws the circle? 1 1 0.1 numerical 1 sage.cs.berkeley.edu+100715050606+V0W2ZP sage.cs.berkeley.edu+100715050606+7wg98W 0 1279170366 1279170366 5 5 8533 8534 8533 360 1 8534 * 0 3192 0 Total Turns Octagon You could draw an Octagon, how far will the character turn in total when it draws a octagon? 1 1 0.1 numerical 1 sage.cs.berkeley.edu+100715050740+sHKzoX sage.cs.berkeley.edu+100715050740+SU0K5z 0 1279170460 1279170460 5 5 8535 8536 8535 360 1 8536 * 0 737 Default for Go Bears! - test yourself The default category for questions shared in context 'Go Bears! - test yourself'. module 8731 sage.cs.berkeley.edu+100218045339+f6FLdC 0 999 3193 0 Predict the behavior Without trying this in Scratch, try to answer the following question: <br /><br /> What does the following set of scripts for the Cat do when you click on the <tt>When I receive Turn1</tt> script? <br /><br /> For this and other self-tests, once you answer, you will be able to see the correct answer and a quick explanation. <br /> 1 Images/Lab01/GoBearsInfiniteLoop.jpg Here, we see an <strong>infinite loop</strong>, or a never-ending loop. Whenever this happens in Scratch, we can always stop it by pressing the <tt>Stop</tt> button at the top right of the Scratch window, just above the stage. <br /><br /> <div style="text-align: center;"><img hspace="0" height="104" border="0" width="116" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab01$@SLASH@$StopGreenFlag.jpg" alt="Stop Button" title="Stop Button" /><br /></div> Why does this happen? Well, when you click on the <tt>When I receive Turn1</tt> script, the Cat says <tt>Go!</tt> for two seconds, and then broadcasts a <tt>Turn2</tt> message. <br /><br /> If there is any character that has a script that responds to the <tt>Turn2</tt> message, it will perform that script. In this case, the Cat has a script that responds to the <tt>Turn2</tt> message, and so it will run the corresponding script. It says <tt>Bears!</tt> and then broadcasts a <tt>Turn1</tt> message. But, it also has a script that responds to the <tt>Turn1</tt> message, which in turn sends a <tt>Turn2</tt> message, and so on. This continues until the scripts are forced to stop. 0 0.1 multichoice 1 sage.cs.berkeley.edu+100218045817+PrmPi7 sage.cs.berkeley.edu+100830014639+1hrPVv 0 1266469097 1283132799 5 161 0 8537,8538,8539,8540 1 1 abc 8537 Nothing happens - this does not work. 0 Actually, it does work and creates what we call an <strong>infinite loop</strong>. <br /> 8538 The Cat says "Go!" and then "Bears!" once. 0 Actually, it does work and creates what we call an <strong>infinite loop</strong>. <br /> 8539 The Cat says "Go!" and then "Bears!" a few times and then stops by itself. 0 Actually, it does work and creates what we call an <strong>infinite loop</strong>. <br /> 8540 The Cat says "Go!" and then "Bears!" until you hit the red Stop button. 1 Yep! We call this an <strong>infinite loop</strong>! 738 Default for Turns - test yourself The default category for questions shared in context 'Turns - test yourself'. module 8749 sage.cs.berkeley.edu+100218052502+boV5P3 0 999 3194 0 Pentagon Turn How far did your character turn (total) when you drew a pentagon? (Write your answer as a number of degrees without writing "degrees") 1 1 0.1 shortanswer 1 sage.cs.berkeley.edu+100218053404+LyNRFX sage.cs.berkeley.edu+100218053438+g0Y5JG 0 1266471244 1266471278 5 5 8541,8542 0 8541 360 1 That's right! 8542 * 0 We don't NEED to turn as much as we did in the square example (360 degrees) but if we used the same format for the pentagon script we DID turn that far! 3195 0 Triangle Turn How far did your character turn (total) when you drew a triangle? (Write your answer as a number of degrees without writing "degrees") 1 1 0.1 shortanswer 1 sage.cs.berkeley.edu+100218053509+sdbLfY sage.cs.berkeley.edu+100218053509+ELKfPt 0 1266471309 1266471309 5 5 8543,8544 0 8543 360 1 That's right! 8544 * 0 We don't NEED to turn as much as we did in the square example (360 degrees) but if we used the same format for the triangle script we DID turn that far! 3196 0 Five Sided Star Turn How far did your character turn (total) when you drew a five sided star? (Write your answer as a number of degrees without writing "degrees") 1 1 0.1 shortanswer 1 sage.cs.berkeley.edu+100218053658+axzhvN sage.cs.berkeley.edu+100218053658+BjuVID 0 1266471418 1266471418 5 5 8545,8546 0 8545 720 1 That's right! We turned around 2 complete times! <br /> 8546 * 0 If we used the same format for the five sided star script as we did for the square we turned around 2 complete times (or 720 degrees)!<br /> 739 Default for IF: what would you expect? The default category for questions shared in context 'IF: what would you expect?'. module 8772 sage.cs.berkeley.edu+100221175715+RO0uHi 0 999 3197 0 What is the value of x at the end of the script? Consider the following script: <br /><br /> <img src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab03$@SLASH@$IfExample.gif" alt="Example 'if' script" title="Example 'if' script" /> <br /><br /> The help screen for the <tt>join</tt> block is provided below, in case you need it. <br /><br /> <img hspace="0" height="348" border="0" width="607" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab03$@SLASH@$JoinHelpScreen.jpg" alt="Help screen for the 'join' block" title="Help screen for the 'join' block" /> <br /><br /> What is the value of <tt>x</tt> at the end of the script above? 1 1 0.1 numerical 1 sage.cs.berkeley.edu+100221175918+0koeOm sage.cs.berkeley.edu+110124080214+H9bq7L 0 1266775158 1295856134 5 706 8547 8548 8547 12 1 8548 * 0 Try again! 3198 0 What is the value of y after the script is run? What is the value of <tt>y</tt> after the script is run? 1 1 0.1 numerical 1 sage.cs.berkeley.edu+100221180112+zzlie0 sage.cs.berkeley.edu+100908033149+HV71PA 0 1266775272 1283916709 5 161 8549 8550 8549 -1 1 8550 * 0 3199 0 What would the character say? What would the character say? 1 1 0.1 numerical 1 sage.cs.berkeley.edu+100221180324+OEsOYi sage.cs.berkeley.edu+100908033320+cwAMsY 0 1266775404 1283916800 5 161 8551 8552 8551 -112 1 Yep! The <tt>join</span> block can be used to join two numbers together and produce one number. 8552 * 0 Sorry, try again! 740 Default for Rock Paper Scissors choices The default category for questions shared in context 'Rock Paper Scissors choices'. module 8780 sage.cs.berkeley.edu+100222180458+2wjOMY 0 999 3200 0 What does the character say if their choice is 1? We want two characters to be able to play the game of <em>Rock, Paper, Scissors</em> against each other. We will do this by making a variable for each character that stores a number. They store a random number between <tt>1</tt> and <tt>3</tt> into this variable. Based on this number, they say the corresponding word. An example run of the code is shown below: <br /><br /> <img hspace="0" height="214" border="0" width="361" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$RockPaperScissorsIntro.jpg" alt="Rock, Paper, Scissors Intro" title="Rock, Paper, Scissors Intro" /> <br /> Based on the diagram above, what does the character say if their choice is <tt>1</tt>? 1 1 0.1 shortanswer 1 sage.cs.berkeley.edu+100222180710+dsJCAa sage.cs.berkeley.edu+100908042536+ZcWfQp 0 1266862030 1283919936 5 161 8553,8554 0 8553 rock 1 8554 * 0 Nope, try again. 3201 0 What does the character say if their choice is 2? Based on the diagram above, what does the character say if their choice is <tt>2</tt>? 1 1 0.1 shortanswer 1 sage.cs.berkeley.edu+100222203927+BHLXFL sage.cs.berkeley.edu+100908042618+eF7hya 0 1266871167 1283919978 5 161 8555,8556 0 8555 paper 1 8556 * 0 Nope, try again! 3202 0 What does the character say if their choice is 3? Based on the diagram above, what does the character say if their choice is <tt>3</tt>? 1 1 0.1 shortanswer 1 sage.cs.berkeley.edu+100222204016+rvavJU sage.cs.berkeley.edu+100908042637+xKzOvX 0 1266871216 1283919997 5 161 8557,8558 0 8557 scissors 1 8558 * 0 Nope, try again! 741 Default for Detecting key pressed The default category for questions shared in context 'Detecting key pressed'. module 8745 sage.cs.berkeley.edu+100323013720+ECBWHJ 0 999 3203 0 Up Arrow Pressed - Which versions work? Which versions shown below provide the same functionality as the <tt>Original</tt> script, where the character will say <tt>Up Arrow Pressed</tt> for two seconds every time the up arrow key is pressed? <br /><br /> <div style="text-align: center;"> <img hspace="0" height="459" border="0" width="771" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$WhenArrowPressedWide.gif" alt="Different versions" title="Different versions" /><br /> </div> 1 We want you to be able to reason about many different ways of doing the same thing. You may not have seen all of these blocks but we want you to practice reasoning through what each block does.<br /> <ul> <li>Version 1 and 2 work as desired.</li> <li>Version 3 and 6 will say the correct thing the first time the up arrow key is pressed but will stop running after that.</li> <li>Version 4 will do nothing unless you are pressing the up arrow key at the same time that you click the green flag.</li> <li>Version 5 will keep saying <tt>Up Arrow Pressed</tt> until you actually press the up arrow key.</li> </ul> 0 0.1 multichoice 1 sage.cs.berkeley.edu+100323014606+O5gMhR sage.cs.berkeley.edu+100901144147+ZvNc4h 0 1269308766 1283352107 5 161 0 8559,8560,8561,8562,8563,8564 0 0 none 8559 Version 1 0.5 8560 Version 2 0.5 8561 Version 3 0 8562 Version 4 0 8563 Version 5 0 8564 Version 6 0 3204 0 Up Arrow Pressed - Which versions work? Which versions shown below provide the same functionality as the <tt>Original</tt> script, where the character will say <tt>Up Arrow Pressed</tt> for two seconds every time the up arrow key is pressed? <br /><br /> <div style="text-align: center;"> <img hspace="0" height="459" border="0" width="771" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$WhenArrowPressedWide.gif" alt="Different versions" title="Different versions" /><br /></div> 1 We want you to be able to reason about many different ways of doing the same thing. You may not have seen all of these blocks before, but we want you to practice reasoning through what each block does.<br /> <ul> <li>Version 1 and 2 work as desired.</li> <li>Version 3 and 6 will say the correct thing the first time the up arrow key is pressed but will stop running after that.</li> <li>Version 4 will do nothing unless you are pressing the up arrow at the same time you click the green flag.</li> <li>Version 5 will keep saying <tt>Up Arrow Pressed</tt> until you actually press the up arrow key.</li> </ul> 0 0.1 multichoice 1 sage.cs.berkeley.edu+100901143951+mVDNK7 sage.cs.berkeley.edu+100901143952+n8v2Sx 0 1283351991 1283351991 161 161 0 8565,8566,8567,8568,8569,8570 0 0 none 8565 Version 1 0.5 8566 Version 2 0.5 8567 Version 3 0 8568 Version 4 0 8569 Version 5 0 8570 Version 6 0 742 Default for Repeat self-test The default category for questions shared in context 'Repeat self-test'. module 8750 sage.cs.berkeley.edu+100323015337+qPq95G 0 999 3205 0 Hip Hip Horray How many times does the script below say "Hip"?<br /><img hspace="0" height="149" border="0" width="168" vspace="0" title="There should be an image here" alt="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$Quizzes$@SLASH@$HipHipHorray.gif" /> 1 1 0.1 numerical 1 sage.cs.berkeley.edu+100323015514+0qjCJ3 sage.cs.berkeley.edu+100323015745+nVftw8 0 1269309314 1269309465 5 5 8571 8572 8571 6 1 8572 * 0 3206 0 Hip Hip Horray 2 How many times does the script below say "Horray"?<br /><img hspace="0" height="149" border="0" width="168" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$Quizzes$@SLASH@$HipHipHorray.gif" alt="There should be an image here" title="There should be an image here" /> 1 1 0.1 numerical 1 sage.cs.berkeley.edu+100323015629+DeYTc5 sage.cs.berkeley.edu+100323015802+CRzEIg 0 1269309389 1269309482 5 5 8573 8574 8573 3 1 8574 * 0 3207 0 Hip Hip Horray 3 How many times does the script below say "Hip"?<br /><br /><img hspace="0" height="182" border="0" width="180" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$Quizzes$@SLASH@$HipHipHorray2.gif" alt="There should be an image here" title="There should be an image here"><br /></img> 1 1 0.1 numerical 1 sage.cs.berkeley.edu+100323015731+qD4zoc sage.cs.berkeley.edu+100323015731+yyn2lG 0 1269309451 1269309451 5 5 8575 8576 8575 0 1 8576 * 0 3208 0 Hip Hip Horray 4 How many times does the script below say "What does this -1 do?"?<br /><br /><img hspace="0" height="96" border="0" width="255" vspace="0" title="There should be an image here" alt="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab01$@SLASH@$repeat-1.gif" /><br /> 1 1 0.1 numerical 1 sage.cs.berkeley.edu+100607163830+5wNNt5 sage.cs.berkeley.edu+100607164109+hVz0nL 0 1275928710 1275928869 5 5 8577 8578 8577 0 1 8578 * 0 743 Default for Broadcast vs. Broadcast and Wait The default category for questions shared in context 'Broadcast vs. Broadcast and Wait'. module 8732 sage.cs.berkeley.edu+100323203242+nAcoZh 0 999 3209 0 Play sound and wait How many times will you hear the <tt>meow</tt> sound when you run the script below? <br /> <img hspace="0" height="88" border="0" width="188" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab01$@SLASH@$Wait$@SLASH@$Wait_Meow_withWait.gif" alt="Play sound and wait" title="Play sound and wait" /> 1 0 0.1 numerical 1 sage.cs.berkeley.edu+100323203737+tlavXS sage.cs.berkeley.edu+100830015637+61VWLQ 0 1269376657 1283133397 5 161 8579 8580 8579 4 1 8580 * 0 3210 0 Play sound without wait How many times will you hear the <tt>meow</tt> sound when you run the script below? <br /> <div style="text-align: left;"><img hspace="0" height="88" border="0" width="125" vspace="0" title="Play sound without wait" alt="Play sound without wait" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab01$@SLASH@$Wait$@SLASH@$WaitMeow_nowait.gif" /><br /> </div> 1 0 0.1 numerical 1 sage.cs.berkeley.edu+100323203911+742G7g sage.cs.berkeley.edu+100830015934+uyWRl0 0 1269376751 1283133574 5 161 8581 8582 8581 1 1 8582 * 0 It doesn't wait for the first meow to finish before starting the next, so you only hear one! 3211 0 Broadcast without wait How many times will you hear the note <tt>60</tt> play when you click on the green flag?<br /><br /><img hspace="0" height="127" border="0" width="359" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab01$@SLASH@$Wait$@SLASH@$Broadcast_nowait.gif" alt="Broadcast without wait" title="Broadcast without wait" /><br /><br /> 1 1 0.1 numerical 1 sage.cs.berkeley.edu+100324021906+y0vke6 sage.cs.berkeley.edu+100830083537+lEYtRR 0 1269397146 1283157337 5 161 8583 8584 8583 3 1 8584 * 0 It won't wait for the first one to finish before starting the second so they will all end up just playing over each other.<br /><br /> 3212 0 Broadcast with wait How many times will you hear the note <tt>60</tt> play when you click on the green flag? <br /> <img hspace="0" height="128" border="0" width="402" vspace="0" title="Broadcast with wait" alt="Broadcast with wait" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab01$@SLASH@$Wait$@SLASH@$Broadcast_wait.gif" /> 1 0 0.1 numerical 1 sage.cs.berkeley.edu+100324021930+ykuRV0 sage.cs.berkeley.edu+100830015559+2NnlCX 0 1269397170 1283133359 5 161 8585 8586 8585 12 1 8586 * 0 3213 0 Chain of broadcasts How many times will the sound <tt>meow</tt> be played when we click the green flag? <br /> <img hspace="0" height="218" border="0" width="188" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab01$@SLASH@$SelfTestBroadcast$@SLASH@$alphabetareceive.gif" alt="Chain of broadcasts" title="Chain of broadcasts" /><br /> 1 1 0.1 numerical 1 sage.cs.berkeley.edu+100629120756+VKzxol sage.cs.berkeley.edu+100830083552+ihvKFn 0 1277813276 1283157352 5 161 8587 8588 8587 1 1 8588 * 0 3214 0 Mismatched broadcasts How many times will the sound <tt>meow</tt> be played when we click the green flag? <br /> <img hspace="0" height="141" border="0" width="188" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab01$@SLASH@$SelfTestBroadcast$@SLASH@$alpha_mismatch.gif" alt="Mismatched broadcasts" title="Mismatched broadcasts" /><br /> 1 1 0.1 numerical 1 sage.cs.berkeley.edu+100629120909+1lB7wG sage.cs.berkeley.edu+100830083606+hCSQ5X 0 1277813349 1283157366 5 161 8589 8590 8589 0 1 8590 * 0 744 Default for Weird cases with Lists The default category for questions shared in context 'Weird cases with Lists'. module 8810 sage.cs.berkeley.edu+100324022906+MTqnXd 0 999 3215 0 Case-sensitive Are the words in a list case-sensitive? Is <tt>Thing</tt> different from <tt>thing</tt>? <br /> <img hspace="0" height="32" border="0" width="177" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab05$@SLASH@$ListTrickies$@SLASH@$CaseSensitive.jpg" alt="Case-sensitive words" title="Case-sensitive words" /> 1 1 0.1 multichoice 1 sage.cs.berkeley.edu+100324023305+7u0Q3b sage.cs.berkeley.edu+100915110929+vI5tf2 0 1269397985 1284548969 5 161 0 8591,8592 1 1 abc 8591 Yes 1 8592 No 0 3216 0 Adding a boolean value What gets added to Scratch (or BYOB) when you run the following script? <br /> <img hspace="0" height="34" border="0" width="176" vspace="0" title="Adding a boolean to a list" alt="Adding a boolean to a list" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab05$@SLASH@$ListTrickies$@SLASH@$AddBoolean.jpg" /> 1 1 0.1 shortanswer 1 sage.cs.berkeley.edu+100324023719+SbUzQM sage.cs.berkeley.edu+100915111536+l7nhDK 0 1269398239 1284549336 5 161 8593,8594 0 8593 false 1 8594 * 0 Try it out! 3217 0 Adding to a non-existent location Assuming that you only have five elements in your <tt>players</tt> list, what would happen if you ran the script below? <br /> <img hspace="0" height="29" border="0" width="243" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab05$@SLASH@$ListTrickies$@SLASH@$NonExistentLocation.jpg" alt="Location does not exist" title="Location does not exist" /> 1 1 0.1 multichoice 1 sage.cs.berkeley.edu+100324024153+knVD6i sage.cs.berkeley.edu+100915111525+SFJ8Rd 0 1269398513 1284549325 5 161 0 8595,8596,8597,8598 1 1 abc 8595 "thing" will be added to the end of the list. 0 8596 "thing" will be added to the beginning of the list. 0 8597 The list will remain unchanged. 1 8598 Blank entries will be added to the list so that the new element can be inserted at the index specified. 0 3218 0 Empty List What happens when you run the script below on a list that has no elements? <br /> <img hspace="0" height="28" border="0" width="154" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab05$@SLASH@$ListTrickies$@SLASH@$EmptyList.jpg" alt="Empty list" title="Empty list" /> 1 1 0.1 multichoice 1 sage.cs.berkeley.edu+100324024452+8Pxknn sage.cs.berkeley.edu+100915111708+Gf64Mm 0 1269398692 1284549428 5 161 0 8599,8600,8601,8602 1 1 abc 8599 The block will report a blank. 1 8600 The block will turn red and there will be an error. 0 8601 The block will return the item that was most recently at the specified index. 0 8602 The block will not run. 0 745 Default for Different Trees Self Test The default category for questions shared in context 'Different Trees Self Test'. module 8901 sage.cs.berkeley.edu+100528040009+HjBje0 0 999 3219 0 How many levels? Someone wrote the following code to draw a tree. When they drew the picture in the center, what number did they put in for the levels argument? In other words, what goes in the blank in the code on the right? <br /> <div style="text-align: center;"><img width="290" vspace="0" hspace="0" height="287" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Recursive_Self_Tests$@SLASH@$TreeCode.jpg" alt="There should be an image here" title="There should be an image here" /> <img width="277" vspace="0" hspace="0" height="333" border="0" src="../../../../file.php/5/Images/Lab11/Recursive_Self_Tests/TreeHowManyLevels.jpg" alt="There should be an image here" title="There should be an image here" /><img width="143" vspace="0" hspace="0" height="70" border="0" src="../../../../file.php/5/Images/Lab11/Recursive_Self_Tests/CallTree.gif" alt="There should be an image here" title="There should be an image here" /><br /> </div> 1 1 0.1 numerical 1 sage.cs.berkeley.edu+100528041114+yRiuWU sage.cs.berkeley.edu+100528041114+11XdlI 0 1275019874 1275019874 5 5 8603 8603 5 1 Yep - Level 0 doesn't draw anything. 3220 0 Negative size What would happen if you changed the argument size to be -100? 1 Try it out in Scratch! 1 0.1 multichoice 1 sage.cs.berkeley.edu+100528042039+onnCwp sage.cs.berkeley.edu+100528042226+2BowEl 0 1275020439 1275020546 5 5 0 8604,8605,8606,8607,8608 1 1 abc 8604 The program will never stop running and a lot of different branches will be drawn 0 8605 It will never stop running and only a single branch will be drawn 0 8606 Nothing - it will work just like if the same positive value was provided 0 8607 The image will be flipped upside down but will otherwise look the same 1 8608 Nothing will be drawn 0 3221 0 Negative levels What would happen if you changed the argument levels to be -4? 1 Try it out in Scratch! 1 0.1 multichoice 1 sage.cs.berkeley.edu+100528042133+19uU2X sage.cs.berkeley.edu+100701214640+kOkZ5v 0 1275020493 1278020800 5 5 0 8609,8610,8611,8612,8613 1 1 abc 8609 The program will never stop running and a lot of different branches will be drawn 0 8610 It will never stop running and there will be no forks in the version of the tree that is drawn 1 8611 Nothing - it will work just like if the same positive value was provided 0 8612 The image will be flipped upside down but will otherwise look the same 0 8613 Nothing will be drawn 0 746 Default for Different Versions of Tree The default category for questions shared in context 'Different Versions of Tree'. module 8902 sage.cs.berkeley.edu+100528042829+ebAY59 0 999 3222 0 Do these all work the same way? Do all of the following programs draw the same tree when called with <span style="font-family: courier new,courier,monospace;">size = 100 <span style="font-family: trebuchet ms,verdana,arial,helvetica,sans-serif;">and </span>level = 4</span>? <br /><img hspace="0" height="293" border="0" width="300" vspace="0" title="There should be an image here" alt="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Recursive_Self_Tests$@SLASH@$TreeCode1.jpg" /> <img hspace="0" height="293" border="0" width="306" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Recurisve_Tree$@SLASH@$Tree2.jpg" alt="There should be an image here" title="There should be an image here" /> <img hspace="0" height="372" border="0" width="303" vspace="0" title="There should be an image here" alt="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Recursive_Self_Tests$@SLASH@$TreeCode3.jpg" /><br /> 1 1 0.1 multichoice 1 sage.cs.berkeley.edu+100528043446+Q3SXjD sage.cs.berkeley.edu+100701185841+ZL21MX 0 1275021286 1278010721 5 5 0 8614,8615,8616,8617,8618,8619 1 0 none 8614 Yes all three work the same way 1 8615 Tree1 and Tree2 work the same 0 8616 Tree1 and Tree3 work the same 0 8617 Tree2 and Tree3 work the same 0 8618 No they all draw something different for the same input 0 8619 I don't know 0 3223 0 Which one do you like best? Which version do you think is the "Best"? <br /><br />When we talk about best we mean:<br /> <ul> <li>Easiest to read</li> <li>Written in the most succinct way</li> <li>Has the fewest (or no) bugs<br /></li> </ul> 1 1 0.1 multichoice 1 sage.cs.berkeley.edu+100528043921+jAcr7G sage.cs.berkeley.edu+100528043921+m3sxts 0 1275021561 1275021561 5 5 0 8620,8621,8622 1 0 none 8620 Tree1 0 This one never stops running if you call Tree1 with a negative level argument. 8621 Tree2 1 We think that this one is best because it can be called with negative numbers as size and will not create an infinite loop (like Tree1 and Tree3). It also doesn't do extra work for the case when <span style="font-family: courier new,courier,monospace;">levels = 0</span> 8622 Tree3 0 This one never stops running if you call Tree3 with a negative level argument.It also has an extra step. Sometimes a base case that does something is necessary. Here we just need to not do anything in the base case.<br /> 747 Default for What was changed? The default category for questions shared in context 'What was changed?'. module 8903 sage.cs.berkeley.edu+100528045258+EOTDeK 0 999 3224 0 Whatchanged1 What did we change to get the following image:<br /><img hspace="0" height="328" border="0" width="339" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Recursive_Self_Tests$@SLASH@$Tree5RecursiveCalls.jpg" alt="There should be an image here" title="There should be an image here" /><br /> 1 1 0.1 multichoice 1 sage.cs.berkeley.edu+100528050001+Enl4zZ sage.cs.berkeley.edu+100530220449+zJWNuR 0 1275022801 1275257089 5 5 0 8623,8624,8625 1 1 abc 8623 We added additional recursive calls to the function and other angle stuff to make it all work out 1 8624 We changed the scaling factor (how much the length decreases each time) 0 8625 We changed the turn amount between each branch 0 3225 0 Whatchanged4 What did we change to get the following image:<br /><img hspace="0" height="125" border="0" width="163" vspace="0" title="There should be an image here" alt="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Recursive_Self_Tests$@SLASH@$Tree4.jpg" /><br /> 1 1 0.1 multichoice 1 sage.cs.berkeley.edu+100530215012+jJ9Cgu sage.cs.berkeley.edu+100530220544+nFDpvP 0 1275256212 1275257144 5 5 0 8626,8627,8628 1 1 abc 8626 We added additional recursive calls to the function and other angle stuff to make it all work out 0 8627 We changed the scaling factor (how much the length decreases each time) 0 8628 We changed the turn amount between each branch 1 3226 0 Whatchanged0 We took the following program and changed it in a bunch of different ways. Then we ran the program with different values of size and level. Your goal is to figure out what we changed in the code to produce each image! Note: We can change the input (the size and the number of levels) without changing the code in the block. The original code and picture (right) are shown below. <br /><img hspace="0" height="290" border="0" width="305" vspace="0" title="There should be an image here" alt="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Recursive_Self_Tests$@SLASH@$TreeCode2.jpg" /> <img hspace="0" height="199" border="0" width="148" vspace="0" title="There should be an image here" alt="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Recursive_Self_Tests$@SLASH@$TreeNormal.jpg" /><br /><br /><br />What did we change to get the following image:<br /><img hspace="0" height="293" border="0" width="328" vspace="0" title="There should be an image here" alt="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Recursive_Self_Tests$@SLASH@$TreeSlantedLeft.jpg" /><br /> 1 1 0.1 multichoice 1 sage.cs.berkeley.edu+100530215305+zsaYjP sage.cs.berkeley.edu+100817192815+tVCDLD 0 1275256385 1282073295 5 5 0 8629,8630,8631 1 1 abc 8629 We added additional recursive calls to the function and other angle stuff to make it all work out 0 8630 We changed the scaling factor (how much the length decreases each time) 0 8631 We changed the turn amount between each branch 1 3227 0 Whatchanged3 What did we change to get the following image:<br /><img hspace="0" height="354" border="0" width="464" vspace="0" title="There should be an image here" alt="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Recursive_Self_Tests$@SLASH@$TreeNoScaling.jpg" /><br /> 1 1 0.1 multichoice 1 sage.cs.berkeley.edu+100530215451+lwXNoC sage.cs.berkeley.edu+100530220527+4A4p5O 0 1275256491 1275257127 5 5 0 8632,8633,8634 1 1 abc 8632 We added additional recursive calls to the function and other angle stuff to make it all work out 0 8633 We changed the scaling factor (how much the length decreases each time) 1 8634 We changed the turn amount between each branch 0 3228 0 Whatchanged2 What did we change to get the following image:<br /><img hspace="0" height="239" border="0" width="331" vspace="0" title="There should be an image here" alt="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Recursive_Self_Tests$@SLASH@$Tree3.jpg" /><br /> 1 1 0.1 multichoice 1 sage.cs.berkeley.edu+100530220043+GQQm4x sage.cs.berkeley.edu+100530220428+oPipee 0 1275256843 1275257068 5 5 0 8635,8636,8637 1 1 abc 8635 We added additional recursive calls to the function and other angle stuff to make it all work out 0 8636 We changed the scaling factor (how much the length decreases each time) 1 8637 We changed the turn amount between each branch 0 748 Default for Where is the base case? The default category for questions shared in context 'Where is the base case?'. module 8917 sage.cs.berkeley.edu+100531192402+uLOGAH 0 999 3229 0 Which block In the image of "say the number from zero to x" function diagram below, we want to know in which block the base case is executed. Select which block below. <br /><img hspace="0" height="1056" border="0" width="816" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Countup$@SLASH@$ReversesSayNumber.jpg" alt="there should be an image here" title="there should be an image here" /> 1 1 0.1 multichoice 1 sage.cs.berkeley.edu+100531192653+ga4jgv sage.cs.berkeley.edu+100531192653+Ezn2k5 0 1275334013 1275334013 5 5 0 8638,8639,8640,8641 1 1 abc 8638 the block where x = 0 1 8639 the block where x = 1 0 8640 the block where x = 2 0 8641 the block where x = 3 0 749 Default for Tracing Code on Paper The default category for questions shared in context 'Tracing Code on Paper'. module 8918 sage.cs.berkeley.edu+100531194415+fiPfBI 0 999 3230 0 Trace a new program This problem deals with a new recursive function shown below. We have shown you diagrams for similar functions. In reality, we wouldn't use such a time consuming diagram to trace through code. Below we've shown a truncated diagram, which only keeps track of the arguments to the function. Try to use this diagram to figure out what order the numbers will be said by the following function when the argument 3 is provided. Type your answer below with spaces between each number that is said. <br /><br /> <div style="margin-left: 40px;"><img hspace="0" height="218" border="0" width="134" vspace="0" title="there should be an image here" alt="there should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab13$@SLASH@$MysteryX.gif" /><br /></div> <br /><img hspace="0" border="0" width="500" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$DownUp$@SLASH@$Simplistic.jpg" alt="There should be an image here" title="There should be an image here" /><br /> 1 1 0.1 shortanswer 1 sage.cs.berkeley.edu+100531195209+jtabTx sage.cs.berkeley.edu+100817194523+LpCAUW 0 1275335529 1282074323 5 5 8642,8643 0 8642 3 2 1 0 1 2 3 1 8643 * 0 750 Default for Considering Exceptional Cases in the Range Function The default category for questions shared in context 'Considering Exceptional Cases in the Range Function'. module 8920 sage.cs.berkeley.edu+100531201109+bDY7CW 0 999 3231 0 Does your program work for the following input The program from the last step (below) is a lot more complicated than the original countdown program that we've been working with. <br /><br /><img width="281" vspace="0" hspace="0" height="56" border="0" title="There should be an image here" alt="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Countup$@SLASH@$FromXtoY.gif" /><br /><br />Does your program work with each of the inputs below? This is ungraded - so just consider each case and select the ones that you caught originally. <br /><br />Once you've finished this self-test go back and revise your function to make it work for all of these input<br /> 1 1 0.1 multichoice 1 sage.cs.berkeley.edu+100531202524+aHmFNo sage.cs.berkeley.edu+100901145808+pzDj2F 0 1275337524 1283353088 5 5 0 8644,8645,8646 0 1 abc 8644 With min=0 and max=3 it says the number 0 through 3 (including 0 and 3) 0.33333 8645 With min = 0 and max = 0, it says the number 0 a single time 0.33333 8646 When the min is bigger than the max, no numbers are said 0.33333 751 Default for Where and how can we change variables? The default category for questions shared in context 'Where and how can we change variables?'. module 8800 sage.cs.berkeley.edu+100603143712+ojWa5N 0 999 3232 0 Can we change y with a command block? We know how to modify variables using the "set" and "change" blocks. The question is if we could write our own blocks to modify variables. <br /><br /><img border="0" width="321" vspace="0" hspace="0" height="34" title="There should be an image here" alt="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$Pass_by_value$@SLASH@$add10_normal_ways.gif" /><br /><br />We've written the block named "add 10 to" that adds 10 to a variable as shown below in the block editor. The variable y is a normal variable. The variable x is a block variable. The big idea is if by changing the value of the block variable x will we be able to change the value of the regular variable y. You probably haven't tried this before, so answer this question based upon what you think Scratch BYOB should have done! (Programming languages are designed by people making exactly these decisions).<br /><br /><img border="0" width="120" vspace="0" hspace="0" height="79" title="There should be an image here" alt="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$Pass_by_value$@SLASH@$add10toY_print.gif" /><br /><br /><img border="0" width="386" vspace="0" hspace="0" height="286" title="There should be an image here" alt="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$Pass_by_value$@SLASH@$add10toX_Command.jpg" /><br /><br />What does the character say when we run the script above? <br /> 1 The Scratch BYOB designers decided that you shouldn't be able to change the regular variable x by changing the block variable y. 1 0.1 multichoice 1 sage.cs.berkeley.edu+100603144310+TdoqxK sage.cs.berkeley.edu+110131021710+H8tEQY 0 1275576190 1296440230 5 511 0 8647,8648,8649 1 1 none 8647 10 0 8648 0 1 8649 I don't know 0 752 Default for Change a regular variable within a block The default category for questions shared in context 'Change a regular variable within a block'. module 8801 sage.cs.berkeley.edu+100603160302+IO1btF 0 999 3233 0 change a global variable We have another idea about how to modify a regular variable inside a block. This time we're not going to pass in an argument. We're just going to have the block editor access our regular variable x. <br /><br /><img border="0" width="120" vspace="0" hspace="0" height="75" title="There should be an image here" alt="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$Accessing_and_changing_global_variables$@SLASH@$add10toX_noArg_called.gif" /><br /><br /><img border="0" width="438" vspace="0" hspace="0" height="408" title="There should be an image here" alt="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$Accessing_and_changing_global_variables$@SLASH@$add10toX_noArguments.jpg" /><br /><br />What would the character say after the script is executed? <br />(think about what you would have decided if you were the Scratch BYOB designers)<br /> 1 This may seem a little funny, but if you access the regular variable directly, then you can modify it, even if it wasn't passed in as an argument. 1 0.1 multichoice 1 sage.cs.berkeley.edu+100603160820+T2UItg sage.cs.berkeley.edu+110131021959+r4Fv20 0 1275581300 1296440399 5 511 0 8650,8651,8652 1 1 abc 8650 10 1 8651 0 0 8652 I don't know 0 753 Default for Non-numeric variables The default category for questions shared in context 'Non-numeric variables'. module 8762 sage.cs.berkeley.edu+100629131316+GirRUF 0 999 3234 0 numeric variables What is the value of variable1 after the green flag is clicked? <br /> <div style="margin-left: 40px;"><img hspace="0" height="71" border="0" width="154" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$variable_types$@SLASH@$variableTypes_-_Copy.gif" alt="There should be an image here" title="There should be an image here" /></div> 1 1 0.1 shortanswer 1 sage.cs.berkeley.edu+100629132130+gCVvTC sage.cs.berkeley.edu+100629132130+OWhRMp 0 1277817690 1277817690 5 5 8653,8654 0 8653 5 1 8654 * 0 3235 0 numeric variables modified What is the value of variable2 after the green flag is clicked? <br /> <div style="margin-left: 40px;"><img hspace="0" height="102" border="0" width="254" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$variable_types$@SLASH@$variableTypes_-_Copy_2_.gif" alt="There should be an image here" title="There should be an image here" /><br /></div> 1 1 0.1 shortanswer 1 sage.cs.berkeley.edu+100629132219+Wu2JzK sage.cs.berkeley.edu+100629132219+TW31VT 0 1277817739 1277817739 5 5 8655,8656 0 8655 8 1 8656 * 0 3236 0 string variables What is the value of variable3 after the green flag is clicked? <br /> <div style="margin-left: 40px;"><img hspace="0" height="72" border="0" width="162" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$variable_types$@SLASH@$variableTypes_-_Copy_3_.gif" alt="There should be an image here" title="There should be an image here" /><br /></div> 1 1 0.1 shortanswer 1 sage.cs.berkeley.edu+100629132308+L4pqvh sage.cs.berkeley.edu+100629132308+ErnzVr 0 1277817788 1277817788 5 5 8657,8658 0 8657 Hello 1 8658 * 0 3237 0 string variables modified What is the value of variable4 after the green flag is clicked? <br /> <div style="margin-left: 40px;"><img hspace="0" height="103" border="0" width="254" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$variable_types$@SLASH@$variableTypes_-_Copy_4_.gif" alt="There should be an image here" title="There should be an image here" /><br /></div> 1 1 0.1 shortanswer 1 sage.cs.berkeley.edu+100629132739+Svek6V sage.cs.berkeley.edu+100629132739+NfiSw8 0 1277818059 1277818059 5 5 8659,8660 0 8659 Helloworld 1 8660 * 0 3238 0 string variables modified with plus What is the value of variable5 after the green flag is clicked? <br />(It is kind of crazy to add 4 to "Hello" - so what this does may feel unexpected and you might need to try it in Scratch to see what it does.)<br /> <div style="margin-left: 40px;"><img hspace="0" height="96" border="0" width="254" vspace="0" title="There should be an image here " alt="There should be an image here " src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$variable_types$@SLASH@$variableTypes_-_Copy_5_.gif" /><br /></div> 1 1 0.1 shortanswer 1 sage.cs.berkeley.edu+100629133400+dj0HlQ sage.cs.berkeley.edu+100629133422+pmRVAV 0 1277818440 1277818462 5 5 8661,8662 0 8661 4 1 8662 * 0 3239 0 numeric variables modified with join What is the value of variable6 after the green flag is clicked? <br /> <div style="margin-left: 40px;"><img hspace="0" height="97" border="0" width="254" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$variable_types$@SLASH@$variableTypes_-_Copy_6_.gif" alt="There should be an image here " title="There should be an image here " /><br /></div> 1 1 0.1 shortanswer 1 sage.cs.berkeley.edu+100629133524+49bXLn sage.cs.berkeley.edu+100629133524+leVxx9 0 1277818524 1277818524 5 5 8663,8664 0 8663 0world 1 8664 * 0 754 Default for How was this made? The default category for questions shared in context 'How was this made?'. module 8792 sage.cs.berkeley.edu+100701155822+2oE4Rg 0 999 3240 0 Which tab should this block go into? Someone made the block below to create a multiplication block that can take three numbers.<br /><br /> <img hspace="0" height="408" border="0" width="439" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$SelfTest_MakeFunction$@SLASH@$Multiply3.jpg" alt="Multiply with three arguments" title="Multiply with three arguments" /> <br /><br /> What option did the person pick when they created this block? <br /><br /> <img hspace="0" height="363" border="0" width="302" vspace="0" title="'make a block' dialog box" alt="'make a block' dialog box" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$SelfTest_MakeFunction$@SLASH@$MakeABlock.jpg" /><br /> 1 1 0.1 multichoice 1 sage.cs.berkeley.edu+100701160329+3GEUOa sage.cs.berkeley.edu+110131012514+ATYTfy 0 1278000209 1296437114 5 134 0 8665,8666,8667,8668,8669,8670,8671,8672,8673,8674 1 0 none 8665 Motion 0 8666 Control 0 8667 Looks 0 8668 Sensing 0 8669 Sound 0 8670 Operators 1 8671 Pen 0 8672 Variables 0 8673 Other 0 8674 List 0 3241 0 What type of block? What type of block did they decide to make? 1 1 0.1 multichoice 1 sage.cs.berkeley.edu+100701160437+omJbqg sage.cs.berkeley.edu+100913151212+LI7TLy 0 1278000277 1284390732 5 161 0 8675,8676,8677 1 0 none 8675 command 0 8676 reporter 1 8677 predicate 0 3242 0 What type of input? What type should the inputs to the function be? <br /> <br /> <img hspace="0" height="425" border="0" width="548" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$SelfTest_MakeFunction$@SLASH@$variableType.jpg" alt="Variable Type" title="Variable Type" /> 1 1 0.1 multichoice 1 sage.cs.berkeley.edu+100701160936+pytyO7 sage.cs.berkeley.edu+110131004355+KzuOWz 0 1278000576 1296434635 5 134 0 8678,8679,8680,8681,8682 1 0 none 8678 Any type 0 8679 Number 1 8680 Text 0 8681 Boolean (T/F) 0 8682 List 0 755 Default for Simulating today The default category for questions shared in context 'Simulating today'. module 8956 sage.cs.berkeley.edu+100710165016+rFR2XD 0 999 3243 0 Applications of Simulations As you've read, simulations can be used in a tremendous number of applications, including scientific discovery, product planning, and education. Which of the following activities benefit the <span style="font-weight: bold;">least </span>from simulation? 1 1 0.1 multichoice 1 sage.cs.berkeley.edu+100710165846+rvCnyK sage.cs.berkeley.edu+100824213525+iAKQxq 0 1278781126 1282685725 511 511 0 8683,8684,8685,8686,8687 1 1 abc 8683 Finding a time to meet up with friends to work on a group project. 1 8684 Forecasting the weather for later in the week. 0 8685 Estimating how the long-term use of a new fertilizer will affect a field and the surrounding area. 0 8686 Preparing soldiers for combat situations. 0 8687 Predicting the spread of a contagious virus. 0 756 SelfTest course pactFakeStamp126385987961153348 0 999 3244 0 <pre> ;; returns the number of vowels in a word (define (num-vowels wd) (cond ((empty? wd) 0) ((vowel? (first wd)) (+ 1 (num-vowels (bf wd)))) (else (num-vowels (bf wd))) )) </pre> <pre> ;; returns the number of vowels in a word (define (num-vowels wd) (cond ((empty? wd) 0) ((vowel? (first wd)) (+ 1 (num-vowels (bf wd)))) (else (num-vowels (bf wd))) )) </pre> 1 0 0 multichoice 1 pactFakeStamp1263859879612268134 pactFakeStamp1263859879612750864 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 0 8688,8689 1 0 123 8688 Tail recursive 0 Nope: The recursive results have 1 added to them in the second case. They are combined by '+'. Try tracing this procedure on a word that has vowels. 8689 Embedded (not tail recursive) 1 Yes: the recursive call is 'embedded' by the '+' procedure. And, the base case doesn't return the whole solution. 3245 0 <pre> ;; returns the number of vowels in a word (define (num-vowels2 wd) (num-vowels2-helper wd 0)) (define (num-vowels2-helper wd so-far) (cond ((empty? wd) so-far) ((vowel? (first wd)) (num-vowels2-helper (bf wd) (+ 1 so- <pre> ;; returns the number of vowels in a word (define (num-vowels2 wd) (num-vowels2-helper wd 0)) (define (num-vowels2-helper wd so-far) (cond ((empty? wd) so-far) ((vowel? (first wd)) (num-vowels2-helper (bf wd) (+ 1 so-far)))) (else (num-vowels2-helper (bf wd) so-far)) )) 1 0 0 multichoice 1 pactFakeStamp1263859879612457124 pactFakeStamp1263859879612918714 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 0 8690,8691 1 0 123 8690 Tail recursive 1 Yes! The answer is kept in the argument 'so-far'. 8691 Embedded 0 Nope: there is no combining of the recursive results! 3246 0 What will be the result of the following expressions? <pre> (keep butfirst '(mike is a teacher)) </pre> What will be the result of the following expressions? <pre> (keep butfirst '(mike is a teacher)) </pre> 1 0 0 multichoice 1 pactFakeStamp1263859879613234317 pactFakeStamp126385987961316540 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 0 8692,8693,8694,8695 1 0 123 8692 () 0 No, Remember, everything is scheme is "true" except <tt>#f</tt> 8693 error 0 No. Remember, everything is scheme is "true" except <tt>#f</tt> 8694 (ike s "" eacher) 0 No: <tt>keep</tt> treats the procedure as a predicate (returning <tt>#t</tt> or <tt>#f</tt>), rather than using its return value. (This is what <tt>every</tt> would have returned). 8695 (mike is a teacher) 1 Right! <tt>butfirst</tt> never returns <tt>#f</tt>, so everything will be kept. 3247 0 <pre> (keep odd? '(1 2 3 four five)) </pre> <pre> (keep odd? '(1 2 3 four five)) </pre> 1 0 0 multichoice 1 pactFakeStamp1263859879613229705 pactFakeStamp1263859879613352775 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 0 8696,8697,8698,8699,8700 1 0 123 8696 () 0 No. When <tt>keep</tt> evaluates <tt>(odd? 'four)</tt>, scheme will generate an error. 8697 (1 3 four five) 0 No. When <tt>keep</tt> evaluates <tt>(odd? 'four)</tt>, scheme will generate an error. 8698 (1 3 five) 0 No. When <tt>keep</tt> evaluates <tt>(odd? 'four)</tt>, scheme will generate an error. 8699 (1 3) 0 No. When <tt>keep</tt> evaluates <tt>(odd? 'four)</tt>, scheme will generate an error. 8700 error 1 Right, when <tt>keep</tt> evaluates <tt>(odd? 'four)</tt>, scheme will generate an error. 3248 0 Give the sentence of triples that corresponds to the word o_xx_xoxo. Give the sentence of triples that corresponds to the word <tt>o_xx_xoxo</tt>. 1 0 0 shortanswer 1 pactFakeStamp1263859879615225364 sage.cs.berkeley.edu+100311182404+gdNS1t 0 1234567890 1268331844 $@NULL@$ $@NULL@$ 8701,8702 0 8701 (o2x x5x oxo oxo 25x xxo o5o x5o) 1 8702 * 0 3249 0 Give the word that corresponds to the sentence of triples (xo3 xx6 o8o xxo ox8 36o xxo 3xo). Give the word that corresponds to the sentence of triples <tt>(xo3 xx6 o8o xxo ox8 36o xxo 3xo)</tt>. 1 0 0 shortanswer 1 pactFakeStamp1263859879615281080 sage.cs.berkeley.edu+100311182532+ap6QnW 0 1234567890 1268331932 $@NULL@$ $@NULL@$ 8703,8704 0 8703 xo_xx_o_o 1 8704 * 0 3250 0 <p> Which of the following sentences, during the course of a normal Tic-Tac-Toe game, might be supplied as an argument to the <tt>choose-win</tt> procedure? <p> Which of the following sentences, during the course of a normal Tic-Tac-Toe game, might be supplied as an argument to the <tt>choose-win</tt> procedure? 1 0 0 multichoice 1 pactFakeStamp1263859879615553403 pactFakeStamp1263859879615733421 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 0 8705,8706,8707,8708,8709 0 0 123 8705 (xx3 oxo oxx) 0 The words in the argument to choose-win are all triples that have one digit and two occurrences of the player whose turn it is. (Think about why (xx3 2xx) won't ever be an argument.) 8706 (123 456) 0 8707 (oo7 oo9) 1 8708 (oxx xox) 0 8709 (xx3 2xx) 0 3251 0 Which expression will simulate rolling a 6-sided die? Which expression will simulate rolling a 6-sided die? 1 0 0 multichoice 1 pactFakeStamp1263859879616412654 pactFakeStamp1263859879616560722 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 0 8710,8711,8712,8713 0 0 123 8710 (random 6) 0 This won't return one of 1, 2, 3, 4, 5, or 6! It will return one of 0, 1, 2, 3, 4, or 5 8711 (random 7) 0 This won't return one of 1, 2, 3, 4, 5, or 6! It will return one of 0, 1, 2, 3, 4, 5, or 6 8712 (+ 1 (random 5)) 0 This won't return one of 1, 2, 3, 4, 5, or 6! It will return one of 1, 2, 3, 4, or 5 8713 (+ 1 (random 6)) 1 Yes. 3252 0 Which expression will return a decimal number between 5 and 7, inclusive? Which expression will return a decimal number between 5 and 7, inclusive? 1 0 0 multichoice 1 pactFakeStamp1263859879617727420 sage.cs.berkeley.edu+100415173819+ScKDeS 0 1234567890 1271353099 $@NULL@$ $@NULL@$ 0 8714,8715,8716,8717,8718 0 0 123 8714 (+ 5 (random 2)) 0 8715 (- (random 8) (random 5)) 0 What happens if both calls to random return 0? 8716 (+ 5 (random 3)) 1 Right. 8717 (- (random 8) 4) 0 What happens if both calls to random return 0? 8718 (- (random 7) (random 4)) 0 What happens if both calls to random return 0? 3253 0 Mutlipleanswer Mutlipleanswer 1 0 0 multichoice 1 pactFakeStamp1263859879617940407 pactFakeStamp1263859879617729650 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 0 8719,8720,8721 0 0 123 8719 frog 1 frog feedback 8720 toad 0 toad feedback 8721 snake 0 snake feedback 3254 0 singleanswer singleanswer 1 0 0 multichoice 1 pactFakeStamp1263859879617866661 pactFakeStamp1263859879617867482 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 0 8722,8723,8724 1 0 123 8722 one 1 one feedback 8723 two 0 two feedback 8724 three 0 three feedback 3255 0 Shortanswer Shortanswer 1 0 0 shortanswer 1 pactFakeStamp1263859879618834201 pactFakeStamp1263859879618532039 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8725,8726 0 8725 Shortanswer 1 optional explanation here! 8726 * 0 optional explanation here! 3256 0 mmc two mmc two 1 0 0 multichoice 1 pactFakeStamp1263859879618702747 pactFakeStamp1263859879618289692 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 0 8727,8728,8729,8730 0 0 123 8727 one (incorrect) 0 one feedback 8728 two (correct) 1 two feedback 8729 three (incorrect) 0 three feedback 8730 four (correct) 0 four feedback 3257 0 Domain: From lecture, we can imagine this problem as <tt>(reduce reduce-function (map map-function input)) </tt>with map-function and reduce-function being the functions we choose to use on the potential input file. Which kind of map-reducer should we Domain: From lecture, we can imagine this problem as <tt>(reduce reduce-function (map map-function input)) </tt>with map-function and reduce-function being the functions we choose to use on the potential input file. Which kind of map-reducer should we use? 1 0 0 multichoice 1 pactFakeStamp1263859879618548859 pactFakeStamp1263859879620128653 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 0 8731,8732,8733 1 0 123 8731 reduce-map-letter 0 No, Thinking about the context of this problem, we can see that we want to be working with whole sentences, so our input to the map-function would be sentences. 8732 reduce-map-word 0 No, Thinking about the context of this problem, we can see that we want to be working with whole sentences, so our input to the map-function would be sentences. 8733 reduce-map-sent 1 Yes! Thinking about the context of this problem, it is easy to see that we want to be working with whole sentences. 3258 0 Mapper-function: Since we want to find the length of the longest sentence, we should use a function that counts the number of words per sentence. Remember, we want a sentence of numbers like <tt>'( 8 3 3 4 2 1 2 9)</tt> to be passed into the reduce-funct Mapper-function: Since we want to find the length of the longest sentence, we should use a function that counts the number of words per sentence. Remember, we want a sentence of numbers like <tt>'( 8 3 3 4 2 1 2 9)</tt> to be passed into the reduce-function. Thus, our choice of a map-function becomes like this: <tt> (map map-function *list of sentences) => (1 2 4 6 9 3 7 2)</tt> How do we do this? 1 0 0 multichoice 1 pactFakeStamp126385987962021397 pactFakeStamp1263859879620759903 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 0 8734,8735,8736,8737,8738 1 0 123 8734 count 1 Yes! Count returns the number of words per sentence. 8735 max 0 No, count returns the number of words per sentence. 8736 word 0 No, count returns the number of words per sentence. 8737 map (lambda (...) ...) 0 No, count returns the number of words per sentence. 8738 reduce (lambda (...) ...) 0 No, count returns the number of words per sentence. 3259 0 Reduce-function: Now, we want to "combine" our list of numbers into a single number. In this problem, we want to find the maximum of the sentence. Once again, we have the form: <tt>(reduce reduce-function '(3 9 2 4 3 9 8 1)) => 9 </tt> Reduce-function: Now, we want to "combine" our list of numbers into a single number. In this problem, we want to find the maximum of the sentence. Once again, we have the form: <tt>(reduce reduce-function '(3 9 2 4 3 9 8 1)) => 9 </tt> 1 0 0 multichoice 1 pactFakeStamp1263859879621941326 pactFakeStamp1263859879621696291 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 0 8739,8740,8741,8742,8743 1 0 123 8739 count 0 max is the correct choice for this, as it will automatically take in 2 arguments and get rid of the smaller number. 8740 max 1 max is the correct choice for this, as it will automatically take in 2 arguments and get rid of the smaller number. 8741 word 0 max is the correct choice for this, as it will automatically take in 2 arguments and get rid of the smaller number. 8742 (lambda (...) ...) 0 While your answer may be correct, max is the correct choice for this, as it will automatically take in 2 arguments and get rid of the smaller number. 8743 reduce (lambda (...) ...) 0 max is the correct choice for this, as it will automatically take in 2 arguments and get rid of the smaller number. 757 Quiz course pactFakeStamp126385987962151813 0 999 3260 0 Define a procedure named <tt>geometric-mean</tt> that, given two numbers as arguments, returns the square root of their product. You will probably want to use the <tt>sqrt</tt> procedure, which takes the square root of a number. Define a procedure named <tt>geometric-mean</tt> that, given two numbers as arguments, returns the square root of their product. You will probably want to use the <tt>sqrt</tt> procedure, which takes the square root of a number. 1 0 0 essay 1 pactFakeStamp1263859879621953385 pactFakeStamp1263859879622591104 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8744 0 3261 0 Consider the following procedure: (define (f a b) (* b (+ 3 a)) ) Determine the value of the expression (f (f 3 4) 5) Consider the following procedure: <pre> (define (f a b) (* b (+ 3 a)) ) </pre> Determine the value of the expression <pre> (f (f 3 4) 5) </pre> 1 0 0 essay 1 pactFakeStamp126385987962256341 sage.cs.berkeley.edu+100218195900+AhkjxY 0 1234567890 1266523140 $@NULL@$ $@NULL@$ 8745 0 3262 0 Assume that a definition of square is written: <pre> (define (square x) (* x x)) </pre> <p> Write a call to the procedure square with the argument 3. Assume that a definition of square is written: <pre> (define (square x) (* x x)) </pre> <p> Write a call to the procedure square with the argument 3. 1 0 0 essay 1 pactFakeStamp1263859879622460314 pactFakeStamp126385987962245209 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8746 0 3263 0 Write a call to the procedure square that will result in the error: <pre> "too few arguments to..." </pre> Write a call to the procedure square that will result in the error: <pre> "too few arguments to..." </pre> 1 0 0 essay 1 pactFakeStamp1263859879622178404 pactFakeStamp1263859879622144552 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8747 0 3264 0 Write a call to the procedure square that will result in the error: <pre> "too many arguments to..." </pre> Write a call to the procedure square that will result in the error: <pre> "too many arguments to..." </pre> 1 0 0 essay 1 pactFakeStamp1263859879622682205 pactFakeStamp1263859879622994282 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8748 0 3265 0 Write a call to the procedure square that will result in the error: <pre> "not a number..." </pre> Write a call to the procedure square that will result in the error: <pre> "not a number..." </pre> 1 0 0 essay 1 pactFakeStamp1263859879623207455 pactFakeStamp1263859879623905374 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8749 0 3266 0 Describe, as completely as possible, the argument values for which <tt>mystery</tt> will return a true value. The answer may be "none". Describe, as completely as possible, the argument values for which <tt>mystery</tt> will return a true value. The answer may be "none". 1 0 0 essay 1 pactFakeStamp1263859879623813785 pactFakeStamp1263859879623153078 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8750 0 3267 0 Describe, as completely as possible, the argument values for which <tt>mystery</tt> will return a false value. The answer may be "none". Describe, as completely as possible, the argument values for which <tt>mystery</tt> will return a false value. The answer may be "none". 1 0 0 essay 1 pactFakeStamp1263859879623656173 pactFakeStamp126385987962396191 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8751 0 3268 0 Describe, as completely as possible, the argument values for which <tt>mystery</tt> will not return any value, but will instead generate an error message. The answer may be "none". Describe, as completely as possible, the argument values for which <tt>mystery</tt> will not return any value, but will instead generate an error message. The answer may be "none". 1 0 0 essay 1 pactFakeStamp1263859879623310241 pactFakeStamp1263859879625666413 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8752 0 3269 0 Write the procedure <tt>to-sentence</tt> using <tt>cond</tt> and without using <tt>if</tt>. Write the procedure <tt>to-sentence</tt> using <tt>cond</tt> and without using <tt>if</tt>. 1 0 0 essay 1 pactFakeStamp1263859879625928490 pactFakeStamp1263859879625612447 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8753 0 3270 0 Write the procedure <tt>to-sentence</tt> using <tt>if</tt> and without using <tt>cond</tt>. Write the procedure <tt>to-sentence</tt> using <tt>if</tt> and without using <tt>cond</tt>. 1 0 0 essay 1 pactFakeStamp1263859879625904817 pactFakeStamp1263859879625190731 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8754 0 3271 0 <p> Using <i>version 2</i> of the <tt>day-span</tt> program, fill in the blank below with a <i>legal</i> date so that the call </p> <pre> (day-span ______ '(may 1)) </pre> <p> returns 0. </p> <p> Using <i>version 2</i> of the <tt>day-span</tt> program, fill in the blank below with a <i>legal</i> date so that the call </p> <pre> (day-span ______ '(may 1)) </pre> <p> returns 0. </p> 1 0 0 essay 1 pactFakeStamp1263859879625396062 pactFakeStamp1263859879625169113 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8755 0 3272 0 <p> Again using <i>version 2</i> of the <tt>day-span</tt> program, fill in the blank below with a <i>legal</i> date so that the call </p> <pre> (day-span ______ '(april 30)) </pre> <p> returns 0. </p> <p> Again using <i>version 2</i> of the <tt>day-span</tt> program, fill in the blank below with a <i>legal</i> date so that the call </p> <pre> (day-span ______ '(april 30)) </pre> <p> returns 0. </p> 1 0 0 essay 1 pactFakeStamp1263859879626938017 pactFakeStamp1263859879626411835 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8756 0 3273 0 <p> Your call causes a crash in version 1 of the <tt>day-span</tt> program. Explain why. </p> <p> Your call causes a crash in version 1 of the <tt>day-span</tt> program. Explain why. </p> 1 0 0 essay 1 pactFakeStamp1263859879626836293 pactFakeStamp1263859879626819801 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8757 0 3274 0 <p> Using <i>version 1</i> of the <tt>day-span</tt> program, fill in the blank below with an <i>illegal</i> date so that the call </p> <pre> (day-span ______ '(april 30)) </pre> <p> returns 0. </p> <p> Using <i>version 1</i> of the <tt>day-span</tt> program, fill in the blank below with an <i>illegal</i> date so that the call </p> <pre> (day-span ______ '(april 30)) </pre> <p> returns 0. </p> 1 0 0 essay 1 pactFakeStamp1263859879627487222 pactFakeStamp1263859879627650908 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8758 0 3275 0 <p> Consider a modified <tt>downup</tt> procedure: <pre> (define (downup wd) (if (<= (count wd) 2) ; 1 was replaced by 2 (se wd) (se wd (downup (bl wd)) wd)) ) </pre><p> Which of the <tt>downup<sub>n</sub></tt> procedures would need to be change <p> Consider a modified <tt>downup</tt> procedure: <pre> (define (downup wd) (if (<= (count wd) 2) ; 1 was replaced by 2 (se wd) (se wd (downup (bl wd)) wd)) ) </pre><p> Which of the <tt>downup<sub>n</sub></tt> procedures would need to be changed to make them give the same results as the new <tt>downup</tt>, and how would it/they change? Change as few of the downup_n procedures as possible. Here are the original versions: <pre> (define (downup1 wd) (se wd)) (define (downup2 wd) (se wd (downup1 (bl wd)) wd)) (define (downup3 wd) (se wd (downup2 (bl wd)) wd)) (define (downup4 wd) (se wd (downup3 (bl wd)) wd)) </pre> 1 0 0 essay 1 pactFakeStamp1263859879627158694 pactFakeStamp1263859879627898415 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8759 0 3276 0 <p> Use the modified version of <tt>downup</tt> from the last question to evaluate the expression <pre> (downup 'clint) </pre> <p> Use the modified version of <tt>downup</tt> from the last question to evaluate the expression <pre> (downup 'clint) </pre> 1 0 0 essay 1 pactFakeStamp1263859879627544295 pactFakeStamp1263859879627383797 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8760 0 3277 0 <p> Consider a solution to the <tt>count-ums</tt> exercise (<i>Simply Scheme</i> exercise 11.2). </p> <pre> (define (count-ums sent) (cond ((empty? sent) 0) ((equal? (first sent) 'um) (+ 1 (count-ums (bf sent)))) (else (count-ums (bf sent))) <p> Consider a solution to the <tt>count-ums</tt> exercise (<i>Simply Scheme</i> exercise 11.2). </p> <pre> (define (count-ums sent) (cond ((empty? sent) 0) ((equal? (first sent) 'um) (+ 1 (count-ums (bf sent)))) (else (count-ums (bf sent))) ) ) </pre> <p> Make a small change to one of the lines in <tt>count-ums</tt> so that for some arguments it returns the right answer and for others it returns a wrong answer. (Indicate which arguments have which results.) </p> 1 0 0 essay 1 pactFakeStamp1263859879628995791 pactFakeStamp1263859879628962701 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8761 0 3278 0 <p> Make a small change to a different line in <tt>count-ums</tt> (the working version) so that for some arguments it returns the right answer and for others it enters an infinite recursion. (Indicate which arguments have which results.) </p> <p> Make a small change to a different line in <tt>count-ums</tt> (the working version) so that for some arguments it returns the right answer and for others it enters an infinite recursion. (Indicate which arguments have which results.) </p> 1 0 0 essay 1 pactFakeStamp1263859879628278822 pactFakeStamp1263859879628952660 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8762 0 3279 0 <p> The following procedure has a bug. Describe it in general. (Remember, don't use the Scheme interpreter.) <pre> ; Return the position of the given word in the given sentence. ; Positions are numbered starting at 1 (to correspond to the ; item procedur <p> The following procedure has a bug. Describe it in general. (Remember, don't use the Scheme interpreter.) <pre> ; Return the position of the given word in the given sentence. ; Positions are numbered starting at 1 (to correspond to the ; item procedure). If the word does not appear in the ; sentence, return #f. (define (position wd sent) (cond ((empty? sent) #f) ((equal? wd (first sent)) 1) (else (+ 1 (position wd (butfirst sent)))) ) ) </pre> 1 0 0 essay 1 pactFakeStamp1263859879630915431 pactFakeStamp1263859879630788818 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8763 0 3280 0 <p> Making as few changes as possible, fix the bug. (You only have to change one line.) </p> <p> Making as few changes as possible, fix the bug. (You only have to change one line.) </p> 1 0 0 essay 1 pactFakeStamp1263859879630245888 pactFakeStamp1263859879630484390 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8764 0 3281 0 <p> The version of the <tt>decimal-value</tt> procedure designed first was <pre> (define (decimal-value roman-numeral) (sum-of-all (digit-values roman-numeral)) ) </pre> <p> When it's given a Roman numeral with a prefix, is the value too high or too low <p> The version of the <tt>decimal-value</tt> procedure designed first was <pre> (define (decimal-value roman-numeral) (sum-of-all (digit-values roman-numeral)) ) </pre> <p> When it's given a Roman numeral with a prefix, is the value too high or too low? Briefly explain. 1 0 0 essay 1 pactFakeStamp1263859879631723282 pactFakeStamp1263859879631716994 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8765 0 3282 0 <p> Without using the Scheme interpreter, determine what version 2 of the Roman Numerals program will return for the following call: </p> <pre>(decimal-value '(i v x))</pre> <p> Without using the Scheme interpreter, determine what version 2 of the Roman Numerals program will return for the following call: </p> <pre>(decimal-value '(i v x))</pre> 1 0 0 essay 1 pactFakeStamp1263859879631249856 pactFakeStamp126385987963146872 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8766 0 3283 0 <p>In the game "Madlibs", participants first produce a list of adjectives. Then these words are substituted into blanks in a story. Since the participants thought up the words without knowing the story, the result can be quite humorous. <p>Write a proce <p>In the game "Madlibs", participants first produce a list of adjectives. Then these words are substituted into blanks in a story. Since the participants thought up the words without knowing the story, the result can be quite humorous. <p>Write a procedure named <tt>madlibs</tt> that is given two sentences as arguments. One sentence will be the list of adjectives chosen by the player of the game. The other will be the story into which the adjectives will be substituted, in sequence. An asterisk <tt>*</tt> will appear at each point in the story where an adjective will go; there will be as many asterisks as there are adjectives. <p>Here's an example. <pre> (madlibs '(sleepy crazy) '(* mary had a * lamb)) </pre> should return <pre> (sleepy mary had a crazy lamb) </pre> 1 0 0 essay 1 pactFakeStamp1263859879632567465 pactFakeStamp1263859879632680580 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8767 0 3284 0 <p> Here is the <tt>prefix-values-removed</tt> procedure from the Roman Numerals code. <pre> (define (prefix-values-removed number-sent) (cond ((empty? number-sent) '( )) ((empty? (bf number-sent)) number-sent) ((and (empty? (bf (bf nu <p> Here is the <tt>prefix-values-removed</tt> procedure from the Roman Numerals code. <pre> (define (prefix-values-removed number-sent) (cond ((empty? number-sent) '( )) ((empty? (bf number-sent)) number-sent) ((and (empty? (bf (bf number-sent))) ; length = 2? (>= (first number-sent) (first (bf number-sent))) ) number-sent) ((not (starts-with-prefix? number-sent)) (se (first number-sent) (prefix-values-removed (bf number-sent)) ) ) ((starts-with-prefix? number-sent) (se (- (first (prefix-values-removed (bf number-sent))) (first number-sent) ) (bf (prefix-values-removed (bf number-sent))) ) ) ) ) </pre> <p> Give a single call to <tt>prefix-values-removed</tt> that, together with all the recursive calls that result, exercises as many of the <tt>cond</tt> result expressions as possible. For example, <tt>(prefix-values-removed '(10 1))</tt> tests only the result expression in the third clause; you can do better than this. Also, explain which <tt>cond</tt> result expressions get exercised by your call. </p> 1 0 0 essay 1 pactFakeStamp1263859879632459389 pactFakeStamp1263859879632371950 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8768 0 3285 0 (every odd? '(1 2 3 4)) produces an error because ... Evaluating (applied-to-all odd? '(1 2 3 4)) would produce an error when its subexpression ___ was evaluated. (every odd? '(1 2 3 4)) produces an error because ... Evaluating (applied-to-all odd? '(1 2 3 4)) would produce an error when its subexpression ___ was evaluated. 1 0 0 essay 1 pactFakeStamp1263859879633331672 pactFakeStamp126385987963364279 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8769 0 3286 0 <p> Given below are possible reasons that evaluation of the expression <tt>(every < '(3 1 4 2))</tt> produces an error. <p> Given below are possible reasons that evaluation of the expression <tt>(every < '(3 1 4 2))</tt> produces an error. 1 0 0 multichoice 1 pactFakeStamp1263859879633284004 pactFakeStamp126385987963353095 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 0 8770,8771,8772 1 1 123 8770 It results in supplying a nonnumber as an argument to the "<" procedure. 1 8771 It results in supplying something that isn't a word or sentence to the "sentence" procedure. 0 8772 It results in supplying the wrong number of arguments to the "<" procedure. 0 3287 0 <p> Given below are possible reasons that evaluation of the expression <tt>(accumulate < '(3 1 4 2))</tt> produces an error. <p> Given below are possible reasons that evaluation of the expression <tt>(accumulate < '(3 1 4 2))</tt> produces an error. 1 0 0 multichoice 1 pactFakeStamp1263859879635108810 pactFakeStamp1263859879635132072 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 0 8773,8774,8775 1 1 123 8773 It results in supplying a nonnumber as an argument to the "<" procedure. 1 8774 It results in supplying something that isn't a word or sentence to the "sentence" procedure. 0 8775 It results in supplying the wrong number of arguments to the "<" procedure. 0 3288 0 <p> We wish to write a procedure <tt>all-doubled</tt> that, given a sentence of numbers, returns the result of doubling all those numbers. Thus <tt>(all-doubled '(-1 15 3))</tt> should return <tt>(-2 30 6)</tt>. <p> Suppose that the following helper proc <p> We wish to write a procedure <tt>all-doubled</tt> that, given a sentence of numbers, returns the result of doubling all those numbers. Thus <tt>(all-doubled '(-1 15 3))</tt> should return <tt>(-2 30 6)</tt>. <p> Suppose that the following helper procedures have been defined: <pre> (define (doubled num) (* 2 num)) (define (first-doubled sent) (* 2 (first sent))) </pre> Choose the correct definition(s) of <tt>all-doubled</tt>. (There may be more than one.) 1 0 0 multichoice 1 pactFakeStamp1263859879636468722 pactFakeStamp1263859879636986115 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 0 8776,8777,8778 1 1 123 8776 (define (all-doubled sent) (every (* 2) sent)) 1 8777 (define (all-doubled sent) (every doubled sent)) 0 8778 (define (all-doubled sent) (every first-doubled sent)) 0 3289 0 <p> Fill in the blanks with one word each so that evaluation of the expression produces the word <tt>ed</tt>. <pre> ( _____ _____ ( _____ _____ '(little child))) </pre> <p> Fill in the blanks with one word each so that evaluation of the expression produces the word <tt>ed</tt>. <pre> ( _____ _____ ( _____ _____ '(little child))) </pre> 1 0 0 essay 1 pactFakeStamp1263859879636384078 pactFakeStamp1263859879636141306 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8779 0 3290 0 <p> Identify, as descriptively and accurately as possible, the type of value returned by the procedure below. Possible types include but are not limited to a triple, a sentence of triples, a square number (1, 2, ..., 9), and a player (<tt>x</tt> or <tt>o <p> Identify, as descriptively and accurately as possible, the type of value returned by the procedure below. Possible types include but are not limited to a triple, a sentence of triples, a square number (1, 2, ..., 9), and a player (<tt>x</tt> or <tt>o</tt>). Assume that the argument for each procedure is a sentence of triples that could be produced by a call to <tt>find-triples</tt>. </p> <p> What type of value is returned by <pre> (define (proc1 triples) (keep (lambda (t) (not (number? t))) (every first triples) ) ) </pre> </p> 1 0 0 essay 1 pactFakeStamp1263859879637840942 pactFakeStamp1263859879637962851 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8780 0 3291 0 <p> What type of value is returned by <pre> (define (proc2 triples) (first-if-any (pivots triples 'x)) ) </pre> </p> <p> What type of value is returned by <pre> (define (proc2 triples) (first-if-any (pivots triples 'x)) ) </pre> </p> 1 0 0 essay 1 pactFakeStamp1263859879637924614 pactFakeStamp1263859879637416675 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8781 0 3292 0 Each of the following words represents a board that could be provided as input to the <tt>ttt</tt> procedure. Which of the boards contains a <i>pivot</i> square for player X? (The answer may be none, or all three.) Each of the following words represents a board that could be provided as input to the <tt>ttt</tt> procedure. Which of the boards contains a <i>pivot</i> square for player X? (The answer may be none, or all three.) 1 0 0 multichoice 1 pactFakeStamp1263859879638152422 pactFakeStamp1263859879638750659 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 0 8782,8783,8784,8785 1 1 123 8782 XO _ _ O _ _ _ X 1 8783 X _ _ XO _ O _ _ 0 8784 O _ _ XXO _ _ _ 0 8785 None of the above contain a pivot (if you select this, make sure you <i>don't</i> select any of the other choices) 0 3293 0 <p>What will</p> <blockquote><pre> (deep-appearances 'joe '((joe) fred) ) </pre></blockquote> <p>return?</p> <p>What will</p> <blockquote><pre> (deep-appearances 'joe '((joe) fred) ) </pre></blockquote> <p>return?</p> 1 0 0 essay 1 pactFakeStamp1263859879640272197 pactFakeStamp1263859879640596277 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8786 0 3294 0 <p>What will </p> <blockquote><pre> (deep-appearances 'joe '(joe (fred (joe joe)) fred joe)) </pre></blockquote> <p>return?</p> <p>What will </p> <blockquote><pre> (deep-appearances 'joe '(joe (fred (joe joe)) fred joe)) </pre></blockquote> <p>return?</p> 1 0 0 essay 1 pactFakeStamp1263859879640499326 pactFakeStamp1263859879640694555 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8787 0 3295 0 <p>Fix the problem (which is within a single case, either base or recursive), by identifying the case, and saying what the changed test and/or return value should be. </p> <p>Fix the problem (which is within a single case, either base or recursive), by identifying the case, and saying what the changed test and/or return value should be. </p> 1 0 0 essay 1 pactFakeStamp1263859879641166193 pactFakeStamp1263859879641981652 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8788 0 3296 0 Evaluate <pre> (butfirst (first (butfirst '(ab cd)))) </pre> Evaluate <pre> (butfirst (first (butfirst '(ab cd)))) </pre> 1 0 0 essay 1 pactFakeStamp1263859879641874552 pactFakeStamp1263859879641864295 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8789 0 3297 0 Consider the following procedure. <pre> (define (weird x) (sentence x '(sentence x 14)) ) </pre> Evaluate <tt>(weird 15)</tt>. Consider the following procedure. <pre> (define (weird x) (sentence x '(sentence x 14)) ) </pre> Evaluate <tt>(weird 15)</tt>. 1 0 0 essay 1 pactFakeStamp1263859879642185850 pactFakeStamp1263859879642424707 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8790 0 3298 0 Write a procedure named <tt>knight</tt> that, given a person's name as argument, returns the name preceded by <tt>sir</tt>. For example, <tt>(knight '(mike clancy))</tt> should return <tt>(sir mike clancy)</tt>. Write a procedure named <tt>knight</tt> that, given a person's name as argument, returns the name preceded by <tt>sir</tt>. For example, <tt>(knight '(mike clancy))</tt> should return <tt>(sir mike clancy)</tt>. 1 0 0 essay 1 pactFakeStamp1263859879642509118 pactFakeStamp126385987964235219 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8791 0 3299 0 <p> Which of the following calls of the first version of the <tt>day-span</tt> procedure produces an error message? (Check all that apply.) <p> Which of the following calls of the first version of the <tt>day-span</tt> procedure produces an error message? (Check all that apply.) 1 0 0 multichoice 1 pactFakeStamp1263859879643394181 pactFakeStamp1263859879643466645 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 0 8792,8793,8794 1 1 123 8792 (day-span '(january 1) '(january 1)) 1 8793 (day-span '(january 1) '(february 1)) 0 8794 (day-span '(january 1) '(march 1)) 0 3300 0 <p> Given below are two versions of a procedure to determine whether one height measurement is greater (taller) than another. A height measurement is a two-word sentence that contains some number of feet and some number of inches; the feet and inches are <p> Given below are two versions of a procedure to determine whether one height measurement is greater (taller) than another. A height measurement is a two-word sentence that contains some number of feet and some number of inches; the feet and inches are accessed by the <tt>feet</tt> and <tt>inches</tt> procedures respectively. <pre> Version 1: (define (is-taller? height1 height2) (cond ((> (feet height1) (feet height2)) #t) ((< (feet height1) (feet height2)) #f) ((> (inches height1) (inches height2)) #t) (else #f) ) ) Version 2: (define (is-taller? height1 height2) (> (+ (* 12 (feet height1)) (inches height1)) (+ (* 12 (feet height2)) (inches height2)) ) ) </pre> Which of the two versions above is more similar to the first version of the <tt>day-span</tt> procedure, and which is more similar to the second version of the <tt>day-span</tt> procedure? Briefly explain your answer. 1 0 0 essay 1 pactFakeStamp1263859879645793161 pactFakeStamp1263859879645339573 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8795 0 3301 0 <p> Write a procedure named <tt>student-grade</tt> that, given a test score between 0 and 100 as argument, returns an indicator of the appropriate grade. (You should use a cond.) <ul> <li>If the score is less than 50, <tt>student-grade</tt> should return <p> Write a procedure named <tt>student-grade</tt> that, given a test score between 0 and 100 as argument, returns an indicator of the appropriate grade. (You should use a cond.) <ul> <li>If the score is less than 50, <tt>student-grade</tt> should return the word <tt>Fail</tt>. </li> <li> If the score is between 50 and 80, inclusive, <tt>student-grade</tt> should return <tt>Pass</tt>. </li> <li> If the score is greater than 80, <tt>student-grade</tt> should return the word <tt>Excellent</tt>. </li> </ul> <p> Your procedure should perform as few comparisons as possible. 1 0 0 essay 1 pactFakeStamp1263859879645790112 pactFakeStamp1263859879645507480 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8796 0 3302 0 Fill in the blank to complete the following alternative definition of the days-in-month procedure. The <tt>item</tt> procedure takes in a number and a word/sentence and returns the corresponding character/word of the word/sentence. <br> <tt>ex) (item 2 '( Fill in the blank to complete the following alternative definition of the days-in-month procedure. The <tt>item</tt> procedure takes in a number and a word/sentence and returns the corresponding character/word of the word/sentence. <br> <tt>ex) (item 2 '(i love cs3)) -> love <br />     (item 3 'code) -> d <br> </tt> <tt> <br>(define (days-in-month month) <br>     (item (month-number month) <br>         ____) )</tt> 1 0 0 essay 1 pactFakeStamp1263859879646732150 pactFakeStamp1263859879646254098 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8797 0 3303 0 How would you explain to someone why the second version of calculating the difference between dates is better? Why is it better? <p>(please limit your answer to < 30 words) How would you explain to someone why the second version of calculating the difference between dates is better? Why is it better? <p>(please limit your answer to < 30 words) 1 0 0 essay 1 pactFakeStamp1263859879647931235 pactFakeStamp1263859879647629473 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8798 0 3304 0 <p> Give a good comment for the following procedure. <pre> (define (mystery sent) (if (empty? sent) sent (sentence (first sent) (mystery (butfirst sent))) ) ) </pre> <p> Give a good comment for the following procedure. <pre> (define (mystery sent) (if (empty? sent) sent (sentence (first sent) (mystery (butfirst sent))) ) ) </pre> 1 0 0 essay 1 pactFakeStamp126385987964790187 pactFakeStamp1263859879647700052 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8799 0 3305 0 <p>Assume that you are working with a "celebrity" program that someone else wrote. This package gives you accessors (or selectors) to work with a "celebrity". You won't change (or even look at) those procedures, but will use them. Some of these accesso <p>Assume that you are working with a "celebrity" program that someone else wrote. This package gives you accessors (or selectors) to work with a "celebrity". You won't change (or even look at) those procedures, but will use them. Some of these accessors include <ul> <li><tt>name</tt>, which takes a single celebrity and returns the name as a single word. For example, if you have stored a celebrity in the variable <tt>cel</tt>, <pre> (name cel) </pre> might return the word <tt>Joe</tt>. </li><li> <tt>hair-color</tt> which takes a celebrity and returns one of the words <tt>blond</tt>, <tt>brown</tt>, <tt>black</tt>, or <tt>red</tt> </li><li>the procedure <tt>movies</tt>, which returns a sentence of movies that the celebrity has been in </li><li>and many other procedures </li></ul> <p> Only by using the accessors can the information about a celebrity be pulled out. </p> <p>Write a recursive procedure <tt>find-michael</tt> which <b>takes a sentence of celebrities</b> and <b>returns a sentence of celebrities</b> who have the name of <tt>michael</tt>. The procedure should return an empty sentence if there are no such named celebrities. 1 0 0 essay 1 pactFakeStamp1263859879650176416 pactFakeStamp1263859879650323785 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8800 0 3306 0 <p>For this question, assume you are still using the celebrity package discussed earlier. <p>Write a recursive procedure <tt>gather-with-hair-color</tt> which takes two arguments: first, a word specifying a hair-color; second, a sentence of celebrities. <p>For this question, assume you are still using the celebrity package discussed earlier. <p>Write a recursive procedure <tt>gather-with-hair-color</tt> which takes two arguments: first, a word specifying a hair-color; second, a sentence of celebrities. The procedure should return a sentence containing the celebrities that have a hair color equal to the first argument. If there are no such celebrities, the procedure should return the empty list. 1 0 0 essay 1 pactFakeStamp1263859879663599844 pactFakeStamp1263859879663423416 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8801 0 3307 0 <p> Give a good comment for the following procedure. <pre> (define (mystery wd) (and (> (count wd) 1) (or (< (decimal-digit-value (first wd)) (decimal-digit-value (second wd))) (mystery (butfirst wd)) ) ) ) </pre> <p> Give a good comment for the following procedure. <pre> (define (mystery wd) (and (> (count wd) 1) (or (< (decimal-digit-value (first wd)) (decimal-digit-value (second wd))) (mystery (butfirst wd)) ) ) ) </pre> 1 0 0 essay 1 pactFakeStamp1263859879665615658 pactFakeStamp1263859879665776860 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8802 0 3308 0 <p> The version of the <tt>decimal-value</tt> procedure designed first was <pre> (define (decimal-value roman-numeral) (sum-of-all (digit-values roman-numeral)) ) </pre> <p> When it's given a Roman numeral with a prefix, is the value too high or too low <p> The version of the <tt>decimal-value</tt> procedure designed first was <pre> (define (decimal-value roman-numeral) (sum-of-all (digit-values roman-numeral)) ) </pre> <p> When it's given a Roman numeral with a prefix, is the value too high or too low? Briefly explain. 1 0 0 essay 1 pactFakeStamp1263859879665876718 pactFakeStamp1263859879665495883 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8803 0 3309 0 <p> In this problem, a positive integer is represented by a sentence of its individual digits. For example, the sentence <tt>(9 8 1 3 1 4 5)</tt> represents the integer 9,813,145 and the sentence <tt>(1 0 0)</tt> represents 100. <p> Write the <tt>plus1</ <p> In this problem, a positive integer is represented by a sentence of its individual digits. For example, the sentence <tt>(9 8 1 3 1 4 5)</tt> represents the integer 9,813,145 and the sentence <tt>(1 0 0)</tt> represents 100. <p> Write the <tt>plus1</tt> procedure, which returns the result of adding 1 to its argument represented in the way just described. Here are some examples. <pre> expression desired result (plus1 '(1)) (2) (plus1 '(8 1 3)) (8 1 4) (plus1 '(9 9 9)) (1 0 0 0) </pre> <p>Consider that, when solving an addition problem by hand, you work with the rightmost digit first, and proceed to the left. 1 0 0 essay 1 pactFakeStamp1263859879666904064 pactFakeStamp1263859879666561562 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8804 0 3310 0 Evaluating <tt>(prefix-values-removed number-sent)</tt> gives <tt>(90 50 9)</tt> as a value. Give two possibilities for <tt>number-sent</tt>. (Hint: they wouldn\'t necessarily represent legal Roman numerals.) Evaluating <tt>(prefix-values-removed number-sent)</tt> gives <tt>(90 50 9)</tt> as a value. Give two possibilities for <tt>number-sent</tt>. (Hint: they wouldn\'t necessarily represent legal Roman numerals.) 1 0 0 essay 1 pactFakeStamp1263859879678966991 pactFakeStamp1263859879678731353 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8805 0 3311 0 Give a single call to <tt>prefix-values-removed</tt> that, together with all the recursive calls that result, exercises as many of the <tt>cond</tt> result expressions as possible. For example, <tt>(prefix-values-removed \'(10 1))</tt> tests only the res Give a single call to <tt>prefix-values-removed</tt> that, together with all the recursive calls that result, exercises as many of the <tt>cond</tt> result expressions as possible. For example, <tt>(prefix-values-removed \'(10 1))</tt> tests only the result expression in the third clause; you can do better than this. Also, explain which <tt>cond</tt> result expressions get exercised by your call. 1 0 0 essay 1 pactFakeStamp1263859879678897380 pactFakeStamp1263859879680547768 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8806 0 3312 0 Recursive calls can contain many different kinds of errors, and can fail in many different ways. Assume that a recursive procedure that you just wrote runs forever -- that is, loops infinitely. <p> Where might the error in your procedure be: Recursive calls can contain many different kinds of errors, and can fail in many different ways. Assume that a recursive procedure that you just wrote runs forever -- that is, loops infinitely. <p> Where might the error in your procedure be: 1 0 0 multichoice 1 pactFakeStamp1263859879680777510 pactFakeStamp126385987968047978 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 0 8807,8808,8809,8810,8811 1 1 123 8807 One of my base cases returns the wrong value 1 8808 The conditional that determines if this call is a base case is wrong 0 8809 My recursive call has the wrong arguments 0 8810 The way I combine the recursive calls to get the final answer is wrong 0 8811 My test case called the procedure incorrectly (i.e., from the STk prompt) 0 3313 0 Assume that a recursive procedure that you just wrote returns the right answer for one test case but returns the wrong one for another test case. <p> Where might the error in your procedure be: Assume that a recursive procedure that you just wrote returns the right answer for one test case but returns the wrong one for another test case. <p> Where might the error in your procedure be: 1 0 0 multichoice 1 pactFakeStamp1263859879681198528 pactFakeStamp1263859879681598139 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 0 8812,8813,8814,8815,8816 1 1 123 8812 One of my base cases returns the wrong value 1 8813 The conditional that determines if this call is a base case is wrong 0 8814 My recursive call has the wrong arguments 0 8815 The way I combine the recursive calls to get the final answer is wrong 0 8816 My second test case called the procedure incorrectly (i.e., from the STk prompt) 0 3314 0 Does the <tt>all-pluralized</tt> procedure work correctly for the domain and range described in the comment above its definition? (This question does not concern whether the actual domain of the procedure is greater than the specified domain, but whether Does the <tt>all-pluralized</tt> procedure work correctly for the domain and range described in the comment above its definition? (This question does not concern whether the actual domain of the procedure is greater than the specified domain, but whether it can be considered to "work" when it has to). 1 0 0 essay 1 pactFakeStamp1263859879682990487 pactFakeStamp1263859879682322431 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8817 0 3315 0 Does the domain and range of <tt>all-pluralized</tt> <i>exactly</i> match the requirements described before the definition? If so, say so. If not, give a call (possibly outside the desired domain) to <tt>all-pluralized</tt> that returns a result outside Does the domain and range of <tt>all-pluralized</tt> <i>exactly</i> match the requirements described before the definition? If so, say so. If not, give a call (possibly outside the desired domain) to <tt>all-pluralized</tt> that returns a result outside of the desired range. 1 0 0 essay 1 pactFakeStamp1263859879682467693 pactFakeStamp1263859879682146992 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8818 0 3316 0 What are legal inputs to the <tt>item</tt> procedure? What are legal inputs to the <tt>item</tt> procedure? 1 0 0 essay 1 pactFakeStamp1263859879685448674 pactFakeStamp126385987968680904 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8819 0 3317 0 <p>Provide a recursive implementation of a new higher-order procedure named <tt>first-position</tt>. <tt>first-position</tt> takes two arguments, a predicate <tt>pred</tt> and a sentence <tt>sent</tt> that contains at least one word that satisfies <tt>pr <p>Provide a recursive implementation of a new higher-order procedure named <tt>first-position</tt>. <tt>first-position</tt> takes two arguments, a predicate <tt>pred</tt> and a sentence <tt>sent</tt> that contains at least one word that satisfies <tt>pred</tt>. <tt>first-position</tt> should return the position in <tt>sent</tt> of the first word to satisfy <tt>pred</tt>. (The position of the first word in <tt>sent</tt> is 1.) For example, <pre> (first-position odd? '(4 1 2 5 9)) </pre> should return 2. 1 0 0 essay 1 pactFakeStamp1263859879686622960 pactFakeStamp126385987968673689 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8820 0 3318 0 <p> Recode the <tt>days-in-month</tt> procedure to use one call each to <tt>first-position</tt>, <tt>item</tt>, and <tt>equal?</tt>, with no other procedure calls. Recall that <tt>days-in-month</tt>, given the name of a month, returns the number of days <p> Recode the <tt>days-in-month</tt> procedure to use one call each to <tt>first-position</tt>, <tt>item</tt>, and <tt>equal?</tt>, with no other procedure calls. Recall that <tt>days-in-month</tt>, given the name of a month, returns the number of days in the month (in a non-leap year). For example, <pre> (days-in-month 'march) </pre> returns 31. You will find the two sentences <pre> (january february march april may june july august september october november december) (31 28 31 30 31 30 31 31 30 31 30 31) </pre> useful. 1 0 0 essay 1 pactFakeStamp1263859879687411942 pactFakeStamp1263859879687450457 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8821 0 3319 0 Recursive calls can contain many different kinds of errors, and can fail in many different ways. Assume that a recursive procedure that you just wrote runs forever -- that is, loops infinitely. <p> Where might the error in your procedure be: Recursive calls can contain many different kinds of errors, and can fail in many different ways. Assume that a recursive procedure that you just wrote runs forever -- that is, loops infinitely. <p> Where might the error in your procedure be: 1 0 0 multichoice 1 pactFakeStamp1263859879687864136 pactFakeStamp1263859879687376659 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 0 8822,8823,8824,8825,8826 1 1 123 8822 One of my base cases returns the wrong value 1 8823 The conditional that determines if this call is a base case is wrong 0 8824 My recursive call has the wrong arguments 0 8825 The way I combine the recursive calls to get the final answer is wrong 0 8826 My test case called the procedure incorrectly (i.e., from the STk prompt) 0 3320 0 Assume that a recursive procedure that you just wrote returns the right answer for one test case but returns the wrong one for another test case. <p> Where might the error in your procedure be: Assume that a recursive procedure that you just wrote returns the right answer for one test case but returns the wrong one for another test case. <p> Where might the error in your procedure be: 1 0 0 multichoice 1 pactFakeStamp1263859879688532435 pactFakeStamp1263859879688154671 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 0 8827,8828,8829,8830,8831 1 1 123 8827 One of my base cases returns the wrong value 1 8828 The conditional that determines if this call is a base case is wrong 0 8829 My recursive call has the wrong arguments 0 8830 The way I combine the recursive calls to get the final answer is wrong 0 8831 My second test case called the procedure incorrectly (i.e., from the STk prompt) 0 3321 0 <p> Suppose that the <tt>cons</tt> procedure is given the lists <tt>(a b)</tt> and <tt>((c) d)</tt> as arguments. What does it return? <p> Suppose that the <tt>cons</tt> procedure is given the lists <tt>(a b)</tt> and <tt>((c) d)</tt> as arguments. What does it return? 1 0 0 essay 1 pactFakeStamp1263859879690789318 pactFakeStamp126385987969030189 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8832 0 3322 0 <p> Suppose that the <tt>append</tt> procedure is given the lists <tt>(a b)</tt> and <tt>((c) d)</tt> as arguments. What does it return? <p> Suppose that the <tt>append</tt> procedure is given the lists <tt>(a b)</tt> and <tt>((c) d)</tt> as arguments. What does it return? 1 0 0 essay 1 pactFakeStamp1263859879708873067 pactFakeStamp1263859879708979192 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8833 0 3323 0 <p> Suppose that the <tt>cons</tt> procedure is given the arguments <tt>(a)</tt> and <tt>b</tt> as arguments. What does it return? <p> Suppose that the <tt>cons</tt> procedure is given the arguments <tt>(a)</tt> and <tt>b</tt> as arguments. What does it return? 1 0 0 essay 1 pactFakeStamp1263859879708741952 pactFakeStamp126385987970863299 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8834 0 3324 0 Here are a few iterations of a fractal. <br>n = 0 <br><img src="http://inst.eecs.berkeley.edu/~cs3/fa08/Mandelbrot/s0.jpg"><br> <br> n = 1 <br><img src="http://inst.eecs.berkeley.edu/~cs3/fa08/Mandelbrot/s1.jpg"> <br> <br>n = 2 <br><img src="http://inst. Here are a few iterations of a fractal. <br>n = 0 <br><img src="http://inst.eecs.berkeley.edu/~cs3/fa08/Mandelbrot/s0.jpg"><br> <br> n = 1 <br><img src="http://inst.eecs.berkeley.edu/~cs3/fa08/Mandelbrot/s1.jpg"> <br> <br>n = 2 <br><img src="http://inst.eecs.berkeley.edu/~cs3/fa08/Mandelbrot/s2.jpg"> <br> <br>n = 20 <br><img src="http://inst.eecs.berkeley.edu/~cs3/fa08/Mandelbrot/s20.jpg"> <br> <br>Write the code to produce it. <br>Hint: Define your own helper draw-square. 1 0 0 essay 1 pactFakeStamp1263859879710802866 pactFakeStamp126385987971055564 0 1234567890 1234567890 $@NULL@$ $@NULL@$ 8835 0 3325 0 Searching Through Time Two labs ago, you saw a few different approaches to the important problem of <em>searching</em>: given a list of numbers, how would you find a certain number that you are interested in? A lot of people are interested in this problem; a lot of companies have people whose jobs are essentially to look through a lot of data and think of algorithms to grab information the user may be looking for <em>as fast as possible</em>. For example, Google has an entire building (or twenty) of people dedicated to arranging the <em>ton</em> of information available on the Internet in various interesting ways, solely so that the search engine can return answers quickly. (In a future lab, you will be implementing a very basic search engine.) Microsoft and Apple create software that organizes the files on a computer in a certain way, so as to make it easier for the computer to quickly find files the user may need or use. <br /><br /> The very first algorithm that we saw for searching was the "walking" approach: we "walk" through the list until we find the number that we want. What kind of runtime would this algorithm have, <em>in the worst-case</em>: would it be constant, linear, or neither? This question may help: if you were having a particularly bad day and the number you wanted was always at the end of the list, how long would it take to find the number if, say, the list was 20 elements long? 200 elements long? 2000 elements long? 1 1 0.1 multichoice 1 sage.cs.berkeley.edu+100927092559+ldOKnB sage.cs.berkeley.edu+100927093530+gQWJKl 0 1285579559 1285580130 161 161 0 8836,8837,8838 1 1 abc 8836 Constant-Time 0 Not quite: the time it takes to search a list scales as the size of the list. This is because the more the numbers in a list, the more the numbers you will have to look at in order to find the number you are interested in.<br /> 8837 Linear-Time 1 Exactly! The time it takes to search a list scales as the size of the list. This is because the more the numbers in a list, the more the numbers you will have to look at in order to find the number you are interested in. 8838 Neither 0 Not quite: the time it takes to search a list scales as the size of the list. This is because the more the numbers in a list, the more the numbers you will have to look at in order to find the number you are interested in.<br /> 758 Default for Which one goes faster? The default category for questions shared in context 'Which one goes faster?'. module 8752 sage.cs.berkeley.edu+100711022612+9xmDS9 0 999 3326 0 Fastest one? <h3>Which one goes faster? </h3>Sometimes we want our songs to go faster or slower. We could do that by changing for how many beats each of the notes plays. Look at the three versions of the song we worked with before. Which one do you think goes fastest? <br /><br /> <table border="1" width="100%"><tbody> <tr> <td width="33%" valign="top"> <p><font size="4">Version 1</font></p> </td> <td width="33%" valign="top"> <p><font size="4">Version 2</font></p> </td> <td width="33%" valign="top"> <p><font size="4">Version 3</font></p> </td> </tr> <tr> <td width="33%" valign="top"><img hspace="0" height="380" border="0" width="221" vspace="0" title="Original Version" alt="Original Version" src="$@FILEPHP@$$@SLASH@$ATDP$@SLASH@$Lab_2$@SLASH@$repeats_tempo3.gif" /><br /> </td> <td width="33%" valign="top"><img hspace="0" height="383" border="0" width="221" vspace="0" title="quiz image" alt="quiz image" src="$@FILEPHP@$$@SLASH@$ATDP$@SLASH@$Lab_2$@SLASH@$repeats_tempo1.gif" /><br /> </td> <td width="33%" valign="top"><img hspace="0" height="389" border="0" width="221" vspace="0" title="quiz image" alt="quiz image" src="$@FILEPHP@$$@SLASH@$ATDP$@SLASH@$Lab_2$@SLASH@$repeats_tempo2.gif" /><br /> </td> </tr></tbody> </table><br /> 1 1 0.1 multichoice 1 sage.cs.berkeley.edu+100711023016+3H19i2 sage.cs.berkeley.edu+100711023251+mE71Eq 0 1278815416 1278815571 5 5 0 8839,8840,8841 1 0 none 8839 Version 1 0 8840 Version 2 1 8841 Version 3 0 3327 0 Slowest one? <p>Which one do you think goes slowest? <br /></p> 1 1 0.1 multichoice 1 sage.cs.berkeley.edu+100711023133+vqnUat sage.cs.berkeley.edu+100711023133+8MJJyt 0 1278815493 1278815493 5 5 0 8842,8843,8844 1 0 none 8842 Version 1 0 8843 Version 2 0 8844 Version 3 1 759 Default for Increasing the tempo The default category for questions shared in context 'Increasing the tempo'. module 8754 sage.cs.berkeley.edu+100711035226+Ph1pXd 0 999 3328 0 tempo0 What is the value of tempo after we double click on the script below? <br /> <div style="margin-left: 40px;"><br /><img hspace="0" height="68" border="0" width="206" vspace="0" src="$@FILEPHP@$$@SLASH@$ATDP$@SLASH@$Lab_2$@SLASH@$drumTempo_no_repeat.gif" alt="quiz image" title="quiz image" /></div> 1 1 0.1 numerical 1 sage.cs.berkeley.edu+100711035442+9O9vKI sage.cs.berkeley.edu+100711035442+7Oy5Ky 0 1278820482 1278820482 5 5 8845 8846 8845 25 1 8846 * 0 3329 0 tempo1 What is the value of tempo after we double click on the script below? <br /> <div style="margin-left: 40px;"><br /><img hspace="0" height="102" border="0" width="206" vspace="0" title="quiz image" alt="quiz image" src="$@FILEPHP@$$@SLASH@$ATDP$@SLASH@$Lab_2$@SLASH@$drumTempo_repeat1.gif" /></div> 1 1 0.1 numerical 1 sage.cs.berkeley.edu+100711035507+u0u8Jq sage.cs.berkeley.edu+100711035507+AFmvGU 0 1278820507 1278820507 5 5 8847 8848 8847 25 1 8848 * 0 3330 0 tempo2 What is the value of tempo after we double click on the script below? <br /> <div style="margin-left: 40px;"><br /><img hspace="0" height="107" border="0" width="206" vspace="0" src="$@FILEPHP@$$@SLASH@$ATDP$@SLASH@$Lab_2$@SLASH@$drumTempo_repeat2.gif" alt="quiz image" title="quiz image" /></div> 1 1 0.1 numerical 1 sage.cs.berkeley.edu+100711035544+4yuXtZ sage.cs.berkeley.edu+100711035544+v7wsnU 0 1278820544 1278820544 5 5 8849 8850 8849 35 1 8850 * 0 3331 0 tempo3 What is the value of tempo after we double click on the script below? <br /> <div style="margin-left: 40px;"><br /><img hspace="0" height="104" border="0" width="206" vspace="0" src="$@FILEPHP@$$@SLASH@$ATDP$@SLASH@$Lab_2$@SLASH@$drumTempo_repeat3.gif" alt="quiz image" title="quiz image" /><br /></div> 1 1 0.1 numerical 1 sage.cs.berkeley.edu+100711035611+CQ67KF sage.cs.berkeley.edu+100711035611+2Mlo3l 0 1278820571 1278820571 5 5 8851 8852 8851 45 1 8852 * 0 3332 0 tempo20 What is the value of tempo after we double click on the script below? <br /> <div style="margin-left: 40px;"><br /><img hspace="0" height="100" border="0" width="206" vspace="0" src="$@FILEPHP@$$@SLASH@$ATDP$@SLASH@$Lab_2$@SLASH@$drumTempo_repeat4.gif" alt="quiz image" title="quiz image" /><br /></div> 1 1 0.1 numerical 1 sage.cs.berkeley.edu+100711035656+2TqSh8 sage.cs.berkeley.edu+100711035656+7xfnhw 0 1278820616 1278820616 5 5 8853 8854 8853 215 1 8854 * 0 760 Default for The Survey The default category for questions shared in context 'The Survey'. module 8736 sage.cs.berkeley.edu+100827221452+kzaD29 0 999 761 Default for Quick Review The default category for questions shared in context 'Quick Review'. module 8997 sage.cs.berkeley.edu+100830015221+Ri2QB8 0 999 3333 0 What does this return? 1 Images/Lab19/HOFQuiz1.png 1 0 shortanswer 1 sage.cs.berkeley.edu+100830015909+bn3vQY sage.cs.berkeley.edu+101101163551+ZJ97vU 0 1283133549 1288629351 441 161 8855 0 8855 algebra purple spaghetti tomato gnu 1 3334 0 2 1 Images/Lab19/HOFQuiz2.png 1 0 shortanswer 1 sage.cs.berkeley.edu+100830024328+Xj4Oop sage.cs.berkeley.edu+100830024328+8gxSlp 0 1283136208 1283136208 441 441 8856 0 8856 blank 1 3335 0 3 1 Images/Lab19/HOFQuiz3.png 1 0 shortanswer 1 sage.cs.berkeley.edu+100830024458+qCE9rn sage.cs.berkeley.edu+100830024458+rx1e31 0 1283136298 1283136298 441 441 8857 0 8857 0 1 3336 0 4 1 Images/Lab19/HOFQuiz4.png 1 0 shortanswer 1 sage.cs.berkeley.edu+100830024806+0LbE5S sage.cs.berkeley.edu+101101163746+Tqj1fW 0 1283136486 1288629466 441 161 8858 0 8858 false 1 3337 0 5 1 Images/Lab19/HOFQuiz5.png 1 0 shortanswer 1 sage.cs.berkeley.edu+100830024857+dmqj2E sage.cs.berkeley.edu+101101163657+LUb0Sp 0 1283136537 1288629417 441 161 8859 0 8859 16 144 0 1 3338 0 6 1 Images/Lab19/HOFQuiz6.png 1 0 shortanswer 1 sage.cs.berkeley.edu+100830025103+uBW995 sage.cs.berkeley.edu+101101163650+lVQbl5 0 1283136663 1288629410 441 161 8860 0 8860 go d sunshi 1 3339 3339 Random Question (Default for Quick Review) 1 0 1 0 random 1 sage.cs.berkeley.edu+100830024203+OSIsxv sage.cs.berkeley.edu+100830024203+tFSwhN 0 1283136123 1283136123 441 441 762 Default for Quick Review 2 The default category for questions shared in context 'Quick Review 2'. module 8998 sage.cs.berkeley.edu+100830035519+ZUdKZO 0 999 3340 0 MC1 Blocks #1 to #4 are being disguised at the "___" section of the block. Which block is it?<br /><br /><br /> 1 Images/Lab19/HOFQuiz7.png 1 0 multichoice 1 sage.cs.berkeley.edu+100830035913+TCDBtU sage.cs.berkeley.edu+101101162914+sjjdAk 0 1283140753 1288628954 441 161 0 8861,8862,8863,8864 1 1 abc 8861 #1 0 8862 #2 1 8863 #3 0 8864 #4 0 3341 0 MC1 Blocks #1 to #4 are being disguised at the "___" block. Which block is it?<br /><br /><br /> 1 Images/Lab19/HOFQuiz7.png 1 0 multichoice 1 sage.cs.berkeley.edu+101101162837+IcSxwJ sage.cs.berkeley.edu+101101162837+WNkgJc 0 1288628917 1288628917 161 161 0 8865,8866,8867,8868 1 1 abc 8865 #1 0 8866 #2 1 8867 #3 0 8868 #4 0 763 Default for Don't use Script Variables Outside of their Script The default category for questions shared in context 'Don't use Script Variables Outside of their Script'. module 8799 sage.cs.berkeley.edu+100901150840+aCG9K1 0 999 3342 0 Script Variable Puzzle 1 What does the character say when you click the green flag? <br /><br /><img width="293" vspace="0" hspace="0" height="162" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab03$@SLASH@$Script_Variables$@SLASH@$scriptVariables_-_Copy.gif" alt="Script variables" title="Script variables" /><br /> 1 1 0.1 multichoice 1 sage.cs.berkeley.edu+100901151323+1usENx sage.cs.berkeley.edu+100901151323+0Qdf7C 0 1283354003 1283354003 5 5 0 8869,8870,8871,8872 1 1 none 8869 10 1 8870 0 0 8871 Nothing 0 8872 Error 0 3343 0 Script Variable Puzzle 2 What does the character say when you click the green flag? <br /><br /><img width="293" vspace="0" hspace="0" height="162" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab03$@SLASH@$Script_Variables$@SLASH@$scriptVariables.gif" alt="Script variables" title="Script variables" /><br /> 1 1 0.1 multichoice 1 sage.cs.berkeley.edu+100901151356+dvbyO6 sage.cs.berkeley.edu+100901151356+rkiCiq 0 1283354036 1283354036 5 5 0 8873,8874,8875,8876 1 1 none 8873 10 1 8874 0 0 8875 Nothing 0 8876 Error 0 3344 0 Script Variable Puzzle 3 What does the character say when you click the green flag? <br /><br /><img width="293" vspace="0" hspace="0" height="162" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab03$@SLASH@$Script_Variables$@SLASH@$scriptVariables_-_Copy_2_.gif" alt="Script variables" title="Script variables" /><br /> 1 1 0.1 multichoice 1 sage.cs.berkeley.edu+100901151431+O1zBmX sage.cs.berkeley.edu+100901151431+YTDQfX 0 1283354071 1283354071 5 5 0 8877,8878,8879,8880 1 1 none 8877 10 0 8878 0 1 8879 Nothing 0 8880 Error 0 3345 0 Script Variable Puzzle 4 What does the character say when you click the green flag? <br /><br /><img width="293" vspace="0" hspace="0" height="163" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab03$@SLASH@$Script_Variables$@SLASH@$scriptVariables_-_Copy_3_.gif" alt="Script variables" title="Script variables" /><br /> 1 1 0.1 multichoice 1 sage.cs.berkeley.edu+100901151502+KFadlk sage.cs.berkeley.edu+100901151502+CEaDWm 0 1283354102 1283354102 5 5 0 8881,8882,8883,8884 1 1 none 8881 10 0 8882 0 1 8883 Nothing 0 8884 Error 0 764 Default for When is the number of times to repeat calculated? The default category for questions shared in context 'When is the number of times to repeat calculated?'. module 8815 sage.cs.berkeley.edu+100901163148+pFIdtL 0 999 3346 0 Repeat Until What numbers does the character say when you run the script below? <br /><br /> <div style="margin-left:40px;"><img width="309" vspace="0" hspace="0" height="251" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab05$@SLASH@$RemoveABC$@SLASH@$RepeatUntil.gif" alt="Repeat Until" title="Repeat Until" /></div> 1 1 0.1 multichoice 1 sage.cs.berkeley.edu+100901163325+tQmngU sage.cs.berkeley.edu+100915231702+Ed2s1l 0 1283358805 1284592622 5 161 0 8885,8886,8887,8888 1 1 none 8885 The numbers 2 through 11. 0 8886 Nothing. 0 8887 Only the number 1. 1 8888 The numbers 1 through 11. 0 3347 0 Repeat What numbers does the character say when you run the script below? <br /><br /> <div style="margin-left:40px;"> <img width="199" vspace="0" hspace="0" height="247" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab05$@SLASH@$RemoveABC$@SLASH@$Repeat.gif" alt="Repeat" title="Repeat" /></div> 1 1 0.1 multichoice 1 sage.cs.berkeley.edu+100901163435+b58CgM sage.cs.berkeley.edu+100915233355+IcNMqA 0 1283358875 1284593635 5 161 0 8889,8890,8891,8892 1 1 none 8889 The numbers 2 through 11. 1 8890 Nothing. 0 8891 Only the number 1. 0 8892 The numbers 1 through 11. 0 765 Default for Changing Variables The default category for questions shared in context 'Changing Variables'. module 8770 sage.cs.berkeley.edu+100908062801+i2DxIx 0 999 3348 0 Under the Boardwalk Let us say that you are trying to create a program that lets you play <em><a href="http://en.wikipedia.org/wiki/Monopoly_%28game%29">Monopoly</a></em> on your computer. You will probably want to use a variable to keep track of how much money you have as the game progresses. In <em>Monopoly</em>, each time you pass the <tt>Go</tt> square, you get $200. If you are keeping track of your money in a variable, which of the following blocks would be most appropriate for changing the amount of money you have when you pass <tt>Go</tt>? 1 1 0.1 multichoice 1 sage.cs.berkeley.edu+100908070046+XUcytp sage.cs.berkeley.edu+100908082334+syp67X 0 1283929246 1283934214 511 161 0 8893,8894,8895 1 1 abc 8893 change MONEY by MONEY + 200 0 <img hspace="0" height="46" border="0" width="248" vspace="0" src="$@FILEPHP@$$@SLASH@$lab3-choice1.png" alt="Choice 1" title="Choice 1" /> 8894 set MONEY to 200 0 <img hspace="0" height="38" border="0" width="147" vspace="0" src="$@FILEPHP@$$@SLASH@$lab3-choice2.png" alt="Choice 2" title="Choice 2" /> 8895 change MONEY by 200 1 <img hspace="0" height="39" border="0" width="172" vspace="0" src="$@FILEPHP@$$@SLASH@$lab3-choice3.png" alt="Choice 3" title="Choice 3" /> 766 Default for Searching Through Time The default category for questions shared in context 'Searching Through Time'. module 8862 sage.cs.berkeley.edu+100927092118+OjJ0Ty 0 999 767 Default for Quiz The default category for questions shared in context 'Quiz'. module 8889 sage.cs.berkeley.edu+101020223747+3B7Uf9 0 999 768 Default for What kind of pattern was alpha? The default category for questions shared in context 'What kind of pattern was alpha?'. module 9021 sage.cs.berkeley.edu+110428174522+hP9Z69 0 999 20 $@NULL@$ ? 11 0 0 1 0 0 1308934625 1308934625 1400 $@NULL@$ $@NULL@$ course $@NULL@$ 20 $@NULL@$ $@NULL@$ $@NULL@$ $@NULL@$ 1 100.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 1.00000 0.00000 0.00000 0 $@NULL@$ 0 0 0 0 1308934625 1308934625 43935 1971 $@NULL@$ 100.00000 0.00000 $@NULL@$ $@NULL@$ 72.35833 0 0 0 0 0 0 $@NULL@$ 0 $@NULL@$ 0 $@NULL@$ $@NULL@$ 43999 1979 $@NULL@$ 100.00000 0.00000 $@NULL@$ $@NULL@$ 77.76667 0 0 0 0 0 0 $@NULL@$ 0 $@NULL@$ 0 $@NULL@$ $@NULL@$ 44005 1975 $@NULL@$ 100.00000 0.00000 $@NULL@$ $@NULL@$ 85.61947 0 0 0 0 0 0 $@NULL@$ 0 $@NULL@$ 0 $@NULL@$ $@NULL@$ 44008 1977 $@NULL@$ 100.00000 0.00000 $@NULL@$ $@NULL@$ 81.53390 0 0 0 0 0 0 $@NULL@$ 0 $@NULL@$ 0 $@NULL@$ $@NULL@$ 44010 1973 $@NULL@$ 100.00000 0.00000 $@NULL@$ $@NULL@$ 69.34000 0 0 0 0 0 0 $@NULL@$ 0 $@NULL@$ 0 $@NULL@$ $@NULL@$ 44220 692 $@NULL@$ 100.00000 0.00000 $@NULL@$ $@NULL@$ 75.51538 0 0 0 0 0 0 $@NULL@$ 0 $@NULL@$ 0 $@NULL@$ $@NULL@$ 44358 1966 $@NULL@$ 100.00000 0.00000 $@NULL@$ $@NULL@$ 76.17000 0 0 0 0 0 0 $@NULL@$ 0 $@NULL@$ 0 $@NULL@$ $@NULL@$ 44378 1974 $@NULL@$ 100.00000 0.00000 $@NULL@$ $@NULL@$ 86.18000 0 0 0 0 0 0 $@NULL@$ 0 $@NULL@$ 0 $@NULL@$ $@NULL@$ 44459 1596 $@NULL@$ 100.00000 0.00000 $@NULL@$ $@NULL@$ 47.50000 0 0 0 0 0 0 $@NULL@$ 0 $@NULL@$ 0 $@NULL@$ $@NULL@$ 44484 1986 $@NULL@$ 100.00000 0.00000 $@NULL@$ $@NULL@$ 69.42000 0 0 0 0 0 0 $@NULL@$ 0 $@NULL@$ 0 $@NULL@$ $@NULL@$ 44607 1992 $@NULL@$ 100.00000 0.00000 $@NULL@$ $@NULL@$ 65.71667 0 0 0 0 0 0 $@NULL@$ 0 $@NULL@$ 0 $@NULL@$ $@NULL@$ 44632 1972 $@NULL@$ 100.00000 0.00000 $@NULL@$ $@NULL@$ 81.52778 0 0 0 0 0 0 $@NULL@$ 0 $@NULL@$ 0 $@NULL@$ $@NULL@$ 44638 1964 $@NULL@$ 100.00000 0.00000 $@NULL@$ $@NULL@$ 50.61429 0 0 0 0 0 0 $@NULL@$ 0 $@NULL@$ 0 $@NULL@$ $@NULL@$ 44658 514 $@NULL@$ 100.00000 0.00000 $@NULL@$ $@NULL@$ 37.50000 0 0 0 0 0 0 $@NULL@$ 0 $@NULL@$ 0 $@NULL@$ $@NULL@$ 44684 1990 $@NULL@$ 100.00000 0.00000 $@NULL@$ $@NULL@$ 79.18981 0 0 0 0 0 0 $@NULL@$ 0 $@NULL@$ 0 $@NULL@$ $@NULL@$ 44721 1963 $@NULL@$ 100.00000 0.00000 $@NULL@$ $@NULL@$ 71.38667 0 0 0 0 0 0 $@NULL@$ 0 $@NULL@$ 0 $@NULL@$ $@NULL@$ 44770 694 $@NULL@$ 100.00000 0.00000 $@NULL@$ $@NULL@$ 82.60476 0 0 0 0 0 0 $@NULL@$ 0 $@NULL@$ 0 $@NULL@$ $@NULL@$ 44781 1616 $@NULL@$ 100.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 0 0 0 0 0 0 $@NULL@$ 0 $@NULL@$ 0 $@NULL@$ $@NULL@$ 45062 1803 $@NULL@$ 100.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 0 0 0 0 0 0 $@NULL@$ 0 $@NULL@$ 0 $@NULL@$ $@NULL@$ 45108 697 $@NULL@$ 100.00000 0.00000 $@NULL@$ $@NULL@$ 66.10000 0 0 0 0 0 0 $@NULL@$ 0 $@NULL@$ 0 $@NULL@$ $@NULL@$ 45147 1970 $@NULL@$ 100.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 0 0 0 0 0 0 $@NULL@$ 0 $@NULL@$ 0 $@NULL@$ $@NULL@$ 45149 2003 $@NULL@$ 100.00000 0.00000 $@NULL@$ $@NULL@$ 70.83333 0 0 0 0 0 0 $@NULL@$ 0 $@NULL@$ 0 $@NULL@$ $@NULL@$ 45205 1984 $@NULL@$ 100.00000 0.00000 $@NULL@$ $@NULL@$ 84.12857 0 0 0 0 0 0 $@NULL@$ 0 $@NULL@$ 0 $@NULL@$ $@NULL@$ 46104 1969 $@NULL@$ 100.00000 0.00000 $@NULL@$ $@NULL@$ 76.00000 0 0 0 0 0 0 $@NULL@$ 0 $@NULL@$ 0 $@NULL@$ $@NULL@$ 47206 2055 $@NULL@$ 100.00000 0.00000 $@NULL@$ $@NULL@$ 95.00000 0 0 0 0 0 0 $@NULL@$ 0 $@NULL@$ 0 $@NULL@$ $@NULL@$ 1401 20 Test Yourself: Go Bears! mod quiz 826 0 $@NULL@$ $@NULL@$ $@NULL@$ 1 10.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 1.00000 0.00000 0.00000 0 $@NULL@$ 0 0 0 0 1308934625 1308934625 1402 20 Turns - test yourself mod quiz 830 0 $@NULL@$ $@NULL@$ $@NULL@$ 1 10.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 1.00000 0.00000 0.00000 0 $@NULL@$ 0 0 0 0 1308934625 1308934625 1403 20 If: What would you expect? mod quiz 836 0 $@NULL@$ $@NULL@$ $@NULL@$ 1 10.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 1.00000 0.00000 0.00000 0 $@NULL@$ 0 0 0 0 1308934625 1308934625 1404 20 Rock, Paper, Scissors: Choices mod quiz 837 0 $@NULL@$ $@NULL@$ $@NULL@$ 1 10.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 1.00000 0.00000 0.00000 0 $@NULL@$ 0 0 0 0 1308934625 1308934625 1405 20 Test Yourself: Detecting a key press mod quiz 829 0 $@NULL@$ $@NULL@$ $@NULL@$ 0 10.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 1.00000 0.00000 0.00000 0 $@NULL@$ 0 0 0 0 1308934625 1309918469 1406 20 Repeat self-test mod quiz 831 0 $@NULL@$ $@NULL@$ $@NULL@$ 1 10.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 1.00000 0.00000 0.00000 0 $@NULL@$ 0 0 0 0 1308934625 1308934625 1407 20 Test Yourself: Different Ways to Broadcast mod quiz 827 0 $@NULL@$ $@NULL@$ $@NULL@$ 0 10.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 1.00000 0.00000 0.00000 0 $@NULL@$ 0 0 0 0 1308934625 1308934625 1408 20 Quiz: Weird Cases mod quiz 842 0 $@NULL@$ $@NULL@$ $@NULL@$ 1 10.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 1.00000 0.00000 0.00000 0 $@NULL@$ 0 0 0 0 1308934625 1308934625 1409 20 Different Trees Self Test mod quiz 846 0 $@NULL@$ $@NULL@$ $@NULL@$ 1 10.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 1.00000 0.00000 0.00000 0 $@NULL@$ 0 0 0 0 1308934625 1308934625 1410 20 Different Versions of Tree mod quiz 847 0 $@NULL@$ $@NULL@$ $@NULL@$ 1 10.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 1.00000 0.00000 0.00000 0 $@NULL@$ 0 0 0 0 1308934625 1308934625 1411 20 What was changed? mod quiz 848 0 $@NULL@$ $@NULL@$ $@NULL@$ 1 10.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 1.00000 0.00000 0.00000 0 $@NULL@$ 0 0 0 0 1308934625 1308934625 1412 20 Where is the base case? mod quiz 849 0 $@NULL@$ $@NULL@$ $@NULL@$ 1 10.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 1.00000 0.00000 0.00000 0 $@NULL@$ 0 0 0 0 1308934625 1308934625 1413 20 Tracing Code on Paper mod quiz 850 0 $@NULL@$ $@NULL@$ $@NULL@$ 1 10.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 1.00000 0.00000 0.00000 0 $@NULL@$ 0 0 0 0 1308934625 1308934625 1414 20 Considering Exceptional Cases in the Range Function mod quiz 851 0 $@NULL@$ $@NULL@$ $@NULL@$ 1 10.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 1.00000 0.00000 0.00000 0 $@NULL@$ 0 0 0 0 1308934625 1308934625 1415 20 Changing regular variables with block variables mod quiz 840 0 $@NULL@$ $@NULL@$ $@NULL@$ 1 10.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 1.00000 0.00000 0.00000 0 $@NULL@$ 0 0 0 0 1308934625 1308934625 1416 20 Change a regular variable within a block mod quiz 841 0 $@NULL@$ $@NULL@$ $@NULL@$ 1 10.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 1.00000 0.00000 0.00000 0 $@NULL@$ 0 0 0 0 1308934625 1308934625 1417 20 Non-numeric variables mod quiz 834 0 $@NULL@$ $@NULL@$ $@NULL@$ 1 10.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 1.00000 0.00000 0.00000 0 $@NULL@$ 0 0 0 0 1308934625 1308934625 1418 20 How was this made? mod quiz 838 0 $@NULL@$ $@NULL@$ $@NULL@$ 1 10.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 1.00000 0.00000 0.00000 0 $@NULL@$ 0 0 0 0 1308934625 1308934625 1419 20 Simulation today mod quiz 852 0 $@NULL@$ $@NULL@$ $@NULL@$ 1 10.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 1.00000 0.00000 0.00000 0 $@NULL@$ 0 0 0 0 1308934625 1308934625 1420 20 Submit-a-Species mod assignment 547 0 $@NULL@$ $@NULL@$ $@NULL@$ 1 100.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 1.00000 0.00000 0.00000 0 $@NULL@$ 0 0 0 0 1308934625 1308934625 1421 20 Homework: Survey mod quiz 828 0 $@NULL@$ $@NULL@$ $@NULL@$ 1 10.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 1.00000 0.00000 0.00000 0 $@NULL@$ 1 0 0 0 1308934625 1308934625 1422 20 Which one goes faster? mod quiz 832 0 $@NULL@$ $@NULL@$ $@NULL@$ 1 10.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 1.00000 0.00000 0.00000 0 $@NULL@$ 0 0 0 0 1308934625 1308934625 1423 20 Increasing the tempo mod quiz 833 0 $@NULL@$ $@NULL@$ $@NULL@$ 1 10.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 1.00000 0.00000 0.00000 0 $@NULL@$ 0 0 0 0 1308934625 1308934625 1424 20 Quick Review mod quiz 853 0 $@NULL@$ $@NULL@$ $@NULL@$ 1 6.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 1.00000 0.00000 0.00000 0 $@NULL@$ 0 0 0 0 1308934625 1308934625 1425 20 Quick Review 2 mod quiz 854 0 $@NULL@$ $@NULL@$ $@NULL@$ 1 10.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 1.00000 0.00000 0.00000 0 $@NULL@$ 0 0 0 0 1308934625 1308934625 1426 20 Don't use Script Variables Outside of their Script mod quiz 839 0 $@NULL@$ $@NULL@$ $@NULL@$ 1 10.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 1.00000 0.00000 0.00000 0 $@NULL@$ 0 0 0 0 1308934625 1308934625 1427 20 Quiz: Loops and Lists mod quiz 843 0 $@NULL@$ $@NULL@$ $@NULL@$ 1 10.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 1.00000 0.00000 0.00000 0 $@NULL@$ 0 0 0 0 1308934625 1308934625 1428 20 Changing Variables mod quiz 835 0 $@NULL@$ $@NULL@$ $@NULL@$ 1 10.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 1.00000 0.00000 0.00000 0 $@NULL@$ 0 0 0 0 1308934625 1308934625 1429 20 Searching Through Time mod quiz 844 0 $@NULL@$ $@NULL@$ $@NULL@$ 1 10.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 1.00000 0.00000 0.00000 0 $@NULL@$ 0 0 0 0 1308934625 1308934625 1430 20 Quiz mod quiz 845 0 $@NULL@$ $@NULL@$ $@NULL@$ 1 10.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 1.00000 0.00000 0.00000 0 $@NULL@$ 0 0 0 0 1308934625 1308934625 1431 20 Card Sorting mod assignment 540 0 $@NULL@$ $@NULL@$ $@NULL@$ 1 100.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 1.00000 0.00000 0.00000 0 $@NULL@$ 0 0 0 0 1308934625 1308934625 1432 20 Card Sorting Discussion mod assignment 541 0 $@NULL@$ $@NULL@$ $@NULL@$ 1 100.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 1.00000 0.00000 0.00000 0 $@NULL@$ 0 0 0 0 1308934625 1308934625 1433 20 Card Sorting Discussion II mod assignment 542 0 $@NULL@$ $@NULL@$ $@NULL@$ 1 100.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 1.00000 0.00000 0.00000 0 $@NULL@$ 0 0 0 0 1308934625 1308934625 1434 20 Card Sorting Discussion III mod assignment 543 0 $@NULL@$ $@NULL@$ $@NULL@$ 1 100.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 1.00000 0.00000 0.00000 0 $@NULL@$ 0 0 0 0 1308934625 1308934625 1435 20 Card Sorting Discussion IV mod assignment 544 0 $@NULL@$ $@NULL@$ $@NULL@$ 1 100.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 1.00000 0.00000 0.00000 0 $@NULL@$ 0 0 0 0 1308934625 1308934625 1436 20 Card Sorting Reflection mod assignment 546 0 $@NULL@$ $@NULL@$ $@NULL@$ 1 100.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 1.00000 0.00000 0.00000 0 $@NULL@$ 0 0 0 0 1308934625 1308934625 1437 20 Card Sorting Discussion V mod assignment 545 0 $@NULL@$ $@NULL@$ $@NULL@$ 1 100.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 1.00000 0.00000 0.00000 0 $@NULL@$ 0 0 0 0 1308934625 1308934625 1438 20 What kind of pattern was alpha? mod quiz 855 0 $@NULL@$ $@NULL@$ $@NULL@$ 1 10.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 1.00000 0.00000 0.00000 0 $@NULL@$ 0 0 0 0 1308934625 1308934625 1439 20 What kind of pattern was Love? mod quiz 856 0 $@NULL@$ $@NULL@$ $@NULL@$ 1 10.00000 0.00000 $@NULL@$ $@NULL@$ 0.00000 1.00000 0.00000 0.00000 0 $@NULL@$ 0 0 0 0 1308934625 1308934625 540 assignment Card Sorting (Physical activity) With your partner, take turns at the following activity: shuffle cards, sort them into A♣ K♣ Q♣ J♣ 10♣ ... 2♣ A♠ K♠ ... 2♠ A♥ K♥ ... 2♥ A♦ K♦ ... 2♦ 0 0 0 0 0 0 0 0 0 online 100000 1316640000 1316035200 100 1287004942 541 assignment Card Sorting Discussion (share) How fast did you do it? (Did you beat the world record?) 0 0 0 0 0 0 0 0 0 online 100000 1316640000 1316035200 100 1287005013 542 assignment Card Sorting Discussion II (share) Think about how fast you could do this if you had the whole class to help. What would your strategy be? 0 0 0 0 0 0 0 0 0 online 100000 1316640000 1316035200 100 1287005059 543 assignment Card Sorting Discussion III (class choice) Look at the other suggestions, and choose one, and predict how fast you could do it. 0 0 0 0 0 0 0 0 0 online 100000 1316640000 1316035200 100 1287005099 544 assignment Card Sorting Discussion IV (Entire class activity) Get up and do it. Your TA will time you starting from when they hand your team the shuffled deck and ending when you hand them back the sorted deck. TAs record how fast you did it. 0 0 0 0 0 0 0 0 0 online 100000 1316640300 1316035500 100 1287005126 545 assignment Card Sorting Discussion V (share) Share a non-computer, real-life example in which the serial portion of some task is smallest (i.e., embarassingly parallel) and greatest (i.e., most difficult to parallelize) 0 0 0 0 0 0 0 0 0 online 100000 1316640300 1316035500 100 1287005195 546 assignment Card Sorting Reflection (reflect) Discuss with your partner whether it was as perfect as you thought it'd be. Do you think it would scale to 50 people? 0 0 0 0 0 0 0 0 0 online 100000 1316640300 1316035500 100 1287005166 547 assignment Submit-a-Species Upload your project from the previous assignment, showing the state of your simulation after 25 time steps. Remember that all three species (sharks, fish, and your species) must all still be alive!<br /><br />Please use your first and last name in your project file. Your file should be named in a format resembling the following: Firstname-Lastname-simulator.ypr. For example, Paul McCartney's simulator would be called <span style="font-style: italic;">Paul-McCartney-simulator.ypr</span>.<br /> 0 0 0 0 0 0 0 0 0 uploadsingle 2097152 1322704800 1311555600 100 1282525811 1011 forum qanda Describe a bug in the 'max' block Try to find the bug in the <tt>max</tt> function below. Then, describe it. <br /><br /> <img hspace="0" height="406" border="0" width="439" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$SelfTest_MakeFunction$@SLASH@$MaxTest.jpg" alt="Bug in the 'max' function" title="Bug in the 'max' function" /><br /> 0 0 0 512000 0 1 1 0 0 1296437041 0 0 0 1012 forum qanda Variable Names in Between What argument (input) names did you use in your function <tt>Between</tt>? What did each one stand for?<br /> (<em>Note</em>: We always want input/variable names that make it easy to guess what the input/variable represents.) 0 0 0 512000 0 0 1 0 0 1284391586 0 0 0 1013 forum qanda Trash or Treasure? <h2>Trash or Treasure?</h2><img vspace="0" hspace="0" height="263" border="0" src="$@FILEPHP@$$@SLASH@$pie.jpg" alt="Apple Pie" title="Apple Pie" style="width: 336px; height: 263px; float: left; display: inline; margin: 4px;" />There will very often be more than one way to solve a particular problem. Let’s consider a chef’s algorithms: recipes. <a href="http://foodnetwork.com/">foodnetwork.com</a> has 261 different recipes for making apple pie. If you’re trying to make a delicious apple pie for someone, you will have multiple recipes that you can use to achieve that goal, but not all of the outcomes will be the same. Many of the recipes will be inferior to others, but you will likely have several high quality recipes to choose from. Does that make them exactly the same? Nope! Different recipes have different trade-offs. Some recipes, for example, may take significantly longer to prepare than others. Others may use more expensive ingredients, or ingredients that you don’t have access to, or obscene amounts of sugar, or a variety of other conditions that impact their usefulness to you. <br /><br />What are some of the trade-offs for other types of algorithms, other than recipes? What do you think some of the trade-offs for computer science algorithms might be? Computer science is loaded with trade-offs and being able to choose between them is a critical skill for creating useful software. <br /><br />Describe two trade-offs that you feel may be relevant to computer science projects, and explain how they may be related (i.e. how or when you may have to trade one for the other). Don't worry about being "correct" as much as having a justifiable connection between two trade-offs. Feel free to (a) mention trade-offs that haven't been mentioned at all yet, (b) expose a new connection between two trade-offs that have already been mentioned separately or (c) if you absolutely can't come up with a pair that hasn't been mentioned, add an new explanation or circumstance to another student's contribution explaining when it might occur. 0 0 0 512000 0 0 1 0 0 1285012493 0 0 0 1014 forum general Comparing Algorithms <h1>Comparing Algorithms</h1> <p>    We all know that computers can be really fast at solving problems: feed a computer a problem that adds several million-digit numbers, and the answer comes out faster than a human has finished the first ten digits. (Well, unless you're one of those <a href="http://en.wikipedia.org/wiki/Mental_calculator">mental calculators</a>.) In fact, that is one of the main motivations behind building computers: there are problems that humans can solve for small values, but once the values become large, it is better to ask a computer to do them instead, since a computer can crunch through calculations faster. Nonetheless, for many applications, speed is essential, and we can't trust a human to perform the calculations: <a href="http://en.wikipedia.org/wiki/Global_Positioning_System">GPS</a>, for example, would be a very different (maybe non-existent) system if a human were continuously determining the position of a plane or of a car.</p> <p>    In these applications, the faster, the better, so if we're faced with two algorithms to perform the same problem, we want to be able to compare which one performs better. Since computers are more useful for large amounts of data, we also want to compare the performances for large inputs. One obvious way to do this is to run both algorithms on large inputs, time each of the algorithms from start to finish, and see which one performs better. (We can also see which algorithm takes up more <em>space</em> in memory, but for today's lab, we will only focus on time.)</p> <p>    Can you think of any other tasks where speed is essential? In other words, can you think of any task that probably would not exist (or that would be very tedious!) if a human were in charge of performing it?</p> 0 0 0 512000 0 2 1 0 0 1297730636 0 0 0 1015 forum eachuser Technology in Your Life Technology has changed all of our lives, even in a short couple of decades. Other than how we look for apartments, how has technology impacted your way of life? Describe an activity that no one else has mentioned that has been changed by technology. Also briefly mention how it used to be done prior to the change in technology and how that method has changed due to technology.<br /><br /><span style="font-weight: bold;">For example:</span><br />How people look for an apartment has changed over the past 20 years. In the past, people might look in the newspaper classifieds or drive around town looking for signs. Today people check Craigslist or another website to quickly locate all of the apartments available in an area.<br /> 0 0 0 512000 0 0 1 0 0 1300332163 0 0 0 1016 forum qanda Debrief Discuss some pros and cons of this model of genomic sequencing, in terms of capturing it as a shortest superstring. <br> <br> Also, think about the pros and cons of the algorithm to solve the shortest superstring problem? 0 0 0 512000 0 0 1 0 0 1271709788 0 0 0 2237 label Welcome! Welcome to the UC-WISE module for CS... <font size="5">Welcome!</font> <br /> Welcome to the UC-WISE module for CS10. This is where we will be hosting all of our lab guides and materials. Feel free to look around and play with the lab materials! The main website (<a href="http://inst.eecs.berkeley.edu/~cs10"><tt>http://inst.eecs.berkeley.edu/~cs10</tt></a>) will host the readings and the semester schedule, while the bSpace site (<a href="http://bspace.berkeley.edu"><tt>http://bspace.berkeley.edu</tt></a>) will be used for announcements and forums.  1283157073 2238 label Learning GoalsGet comfortable with the Scratch use... <table width="100%" border="2" rules="none"><tbody><tr><td><strong>Learning Goals</strong><ul><li>Get comfortable with the Scratch user interface.</li><li>Learn to use <tt>Broadcast</tt> blocks to communicate between sprites and make a movie.</li><li>Get experience debugging using single-step.</li><li>Learn to download, remix and re-post projects on the Scratch website.</li></ul></td></tr></tbody></table> 1285572473 2239 label User Interface Detective Work <strong>User Interface Detective Work</strong> 1283155727 2240 label Broadcast <strong>Broadcast</strong> 1283155746 2241 label Homework <strong>Homework</strong> 1283155765 2242 label Optional Sections for Fun <strong>Optional Sections for Fun</strong> 1283159341 2243 label Learning Goals Learn to use key listene... <table border="2" width="100%"> <tbody> <tr> <td width="100%" valign="top"> <strong>Learning Goals</strong> <ul> <li>Learn to use key listeners to move the characters around the screen.</li> <li>Learn to use the movement and drawing commands in Scratch to draw complex images and geometric shapes.</li> <li>Learn to use variables that change dynamically within a program.</li> <li>Use layers of abstraction in programs to draw complex images.</li> </ul> </td> </tr> </tbody> </table> 1283915214 2244 label Game controls <strong>Game controls</strong> 1283350393 2245 label Drawing <strong>Drawing</strong> 1283350438 2246 label Variables <strong>Variables</strong> 1283350458 2247 label Homework <strong>Homework</strong> 1283350489 2248 label Learning Goals Learn to use the if blo... <table border="2" width="100%"> <tbody> <tr> <td width="100%" valign="top"> <strong>Learning Goals</strong><br /> <ul> <li> Learn to use the <tt>if</tt> block in the context of <tt>forever</tt> loops and when working with variables.</li> <li> Learn to use the <tt>random</tt> block to generate randomness in a game.<br /></li> </ul> </td> </tr> </tbody> </table> 1285570843 2249 label Review: 'Change' versus 'Set' Review: 'Change' versus 'Set' 1283933023 2250 label The If Block The <tt>If</tt> Block 1283915810 2251 label Random Random 1268864878 2252 label Number Guessing Game Number Guessing Game 1266861650 2253 label Rock, Paper, Scissors Rock, Paper, Scissors 1283919583 2254 label Homework Homework 1266872219 2255 label Learning Goals Discover how to use the ... <table width="100%" border="2"> <tbody> <tr> <td width="100%" valign="top"> <strong>Learning Goals</strong> <ul> <li>Discover how to use the BYOB block interface to</li> <ul> <li>Create different shaped blocks.</li> <li>Create inputs of different types.</li> <li>Create inputs with initial values.</li> </ul> <li>Employ blocks and data abstraction to break problems down into smaller problems and thus write more beautiful and elegant code.</li> <li>Explore some of the complexities of managing block variables.</li> </ul> </td> </tr> </tbody> </table> 1285570900 2256 label The Basics of BYOB The Basics of BYOB 1284334960 2257 label Predicates Predicates 1284390916 2258 label Variables Variables 1283354136 2259 label Functions make code easier to understand Functions make code easier to understand 1275408526 2260 label Homework Homework 1283351870 2261 label Learning Goals Practice writing and rea... <table width="100%" border="2"> <tbody> <tr> <td width="100%" valign="top"> <strong>Learning Goals</strong> <ul> <li>Practice writing and reading functions with different input types.</li> <li>Determine how to break problems down into individual functions.</li> <li>Gain experience working with a new data structure and the large repository of blocks that work on this data structure.</li> <li>Develop the techniques and functions to draw a game board.</li> </ul> </td> </tr> </tbody> </table> 1285570944 2262 label Introduction to Lists Introduction to Lists 1284546880 2263 label Lists and Sentences: The Index Variable Pattern Lists and Sentences: The Index Variable Pattern 1284557450 2264 label Lists as Arguments Lists as Arguments 1284557478 2265 label Learning Goals Solidify understanding of wh... <table width="100%" border="2"><tbody><tr><td width="100%" valign="top"><strong>Learning Goals</strong><ul> <li>Solidify understanding of what an algorithm is and why they’re important to computer science and other fields.</li> <li>Gain a basic understanding of why certain algorithms perform better than others.</li> <li>There’s often more than one way to solve the same problem. Certain solutions will be superior to others, but very often choosing a solution will require evaluating a list of trade-offs relevant to your particular situation.</li> <li>Practice implementing algorithms that were discussed verbally.</li> <li>Memoization is a technique that can be used for improving the performance of algorithms with repeated calculations at the expense of a higher memory requirement.</li> <li>Hiding algorithmic details behind a layer of abstraction makes it easier to upgrade or adjust your implementation in the future.<br /></li> </ul></td></tr></tbody></table> 1285572506 2266 label Learning Goals Get more practice with mak... <table border="2" width="100%"><tbody> <tr> <td width="100%" valign="top"> <strong>Learning Goals</strong> <ul> <li>Get more practice with making Lists, accessing elements and inserting items.</li> <li>Learn patterns of looping over an entire list or part of a list.</li> <li>Write and analyze code that sorts a list.</li> </ul> </td> </tr></tbody> </table> 1285572434 2267 label More Practice With Lists: Game Board More Practice With Lists: Game Board 1285176534 2268 label Sorting a List Sorting a List 1284560433 2269 label Drawing a Game Board Drawing a Game Board 1275500033 2270 label Homework Homework 1283356411 2271 label Introduction Introduction 1285573147 2272 label Timing Experiments Timing Experiments 1285575540 2273 label TODO Make sure that you look at the concurrency ex... TODO Make sure that you look at the concurrency exercises from Lab 2. 1281996282 2274 label Learning GoalsIn Scratch / BYOB what a... <table border="1" width="100%"><tbody> <tr> <td width="100%" valign="top"><span style="font-weight: bold;">Learning Goals</span><br /><br />In Scratch / BYOB what are the issues / facilities to do parallel work, and how does the machine work? <ul> <li>A single sprite has control blocks which appear to respond in parallel (e.g., multiple "when green flag, do...", "when space is clicked, do...", "when I receive broadcast", etc.)</li> <li>Multiple sprites only exacerbate the problem, and race conditions could occur (e.g., what if multiple sprites tried to paint the screen their color all at the same time?)</li> <li>What happens when multiple signals are sent to the same "when I receive broadcast" block, do all get through? [yes if Broadcast and wait, no (but consistent) if Broadcast and Edit->Thread Safe Scripts checked, no (but inconsistent) if Edit->Thread Safe Scripts unchecked]</li> <li>When we call "launch", does that mean another worker starts up? [answer: yes and no]</li> <li>The meta learning goal for this part is for you to develop an accurate mental model of how Scratch handles concurrency. This is so you avoid race conditions and deadlock, and so that you can fully exploit it to your benefit!</li> </ul> </td> </tr></tbody> </table><br /> 1294983630 2275 label Activities <span style="font-weight: bold;">Activities </span> 1285958445 2276 label Background; fun sans-computer activities Background; fun sans-computer activities 1287172481 2277 label Scratch... you got some speed, man? Scratch... you got some speed, man? 1287005270 2278 label Scratch... don't all talk at once! Scratch... don't all talk at once! 1287172471 2279 label Scratch... some details to form a mental model Scratch... some details to form a mental model 1287173198 2280 label Learning Goals Explore the idea of rep... <table width="100%" border="2"> <tbody> <tr> <td width="100%" valign="top"> <strong>Learning Goals</strong> <ul> <li>Explore the idea of representing a problem in terms of itself.</li> <li>Practice planning and coding recursive blocks.</li> </ul> </td> </tr> </tbody> </table><br /> 1287946368 2281 label Tree Recursion Tree Recursion 1275263081 2282 label Fractals Fractals 1286207855 2316 label A Survey A Survey 1310488203 2283 label Linear Recursion Linear Recursion 1275263106 2284 label Practice going from iteration to recursion and bac... Practice going from iteration to recursion and back 1283359491 2285 label Learning Goals Review the concept of r... <table width="100%" border="2"> <tbody> <tr> <td width="100%" valign="top"> <strong>Learning Goals</strong> <ul> <li>Review the concept of recursion and the process for creating recursive blocks.</li> <li>Write reusable code that can be used in many applications.</li> <li>Improve the recursive thinking process with some applied recursive activities.</li> </ul> </td> </tr></tbody> </table> 1287946446 2286 label Recursion Warm-up Recursion Warm-up 1276502537 2287 label Applications of Recursion Applications of Recursion 1276502626 2288 label Learning Goals Comput... <table width="100%" border="2"><tbody> <tr> <td width="100%" valign="top"> <strong>Learning Goals</strong> <ul> <li>Computer science is about more than computing prime numbers and solving equations. It has tremendous applications outside of the field of computing but has also created some fantastic new possibilities within the field as computing has evolved.</li> <li>In its short lifetime, computing has totally transformed the modern world.</li> <li>Become familiar with the anatomy of a search engine and how large amounts of data can be handled quickly.<br /></li> </ul> </td> </tr></tbody> </table> 1287946475 2289 label How Life Has Changed How Life Has Changed 1277274368 2290 label Example: Google Example: Google 1277277586 2291 label Learning Goals Gain a... <table width="100%" border="2"><tbody> <tr> <td width="100%" valign="top"> <strong>Learning Goals</strong> <ul> <li>Gain an appreciation for the importance of simulations in scientific discovery.</li> <li>Learn about some modern applications of scientific simulations.</li> </ul> </td> </tr></tbody> </table> 1287946496 2292 label Real-world simulations Real-world simulations 1278451013 2293 label Simulations in Scratch Simulations in Scratch 1278451143 2294 label Background Reading Background Reading 1269723382 2295 label Introducing the Problem Introducing the Problem 1269726110 2296 label The Computational Solution The Computational Solution 1271102250 2297 label Debrief Debrief 1271102274 2298 label Tools Sprite Tools Sprite 1279264157 2299 label Introduction Introduction 1275023164 2300 label Map Map 1275010555 2301 label Keep Keep 1275016937 2302 label Combine Combine 1275020470 2303 label Cascade Cascade 1276282382 2304 label Tic-Tac-Toe Tic-Tac-Toe 1278661900 2305 label Learning Goals <b>Learning Goals</b> 1294864758 2306 label Digital devices, systems, and the networks tha... <ul> <li>Digital devices, systems, and the networks that interconnect them enable and foster computational approaches to solving problems. (this is from AP's big ideas section VI)</li> <li><em>MapReduce</em> is a particularly nice example of a distributed computing pattern, and the facility to write (and debug, and test, and evaluate) programs in our simplified MapReduce abstraction.</li> </ul> 1294864735 2307 label MapReduce Distributed Computing Pattern <b><i>MapReduce</i> Distributed Computing Pattern</b> 1294865092 2308 label Let's start solving problems with MapReduce! <b>Let's start solving problems with MapReduce!</b> 1294865456 2309 label Please complete the following two surveys before ... Please complete the following two surveys before taking the online final. Show your GSI the completed screens so that we can confirm that you finished them. Thanks! 1303926663 2310 label Extras! (A great place for new ideas!) <font size="5">Extras! (A great place for new ideas!) </font> 1268103335 2311 label Concurrency in the game of tag Concurrency in the game of tag 1271086239 2312 label Trickiness Trickiness 1275581398 2313 label Changing variables using block variables Changing variables using block variables 1275580684 2314 label Changing variables by accessing a variable from wi... Changing variables by accessing a variable from within the block editor 1275580717 2315 label Colleen wants to add more stuff here, but needs to... Colleen wants to add more stuff here, but needs to see "Bug 21: Recreating an old variable is disallowed" resolved before continuing. 1275584831 826 quiz Test Yourself: Go Bears! 0 0 1 1 0 0 1 2 4652015 0 0 1 3193,0 0 10 0 1283159273 0 0 0 0 3433 3193 0 1035 826 0 11 827 quiz Test Yourself: Different Ways to Broadcast 0 0 1 1 0 0 1 2 4652015 0 0 1 3209,3210,3212,3211,3213,3214,0 0 0 0 1283159289 0 0 0 0 3434 3209 0 3435 3210 0 3436 3211 0 3437 3212 0 3438 3213 0 3439 3214 0 1036 827 0 1 828 quiz Homework: Survey This survey is being used anonymously to identify patterns in attrition in CS10. We love the course and we can't figure out why anyone would want to drop it! Please fill out the paper form of the waiver before completing this survey. 0 0 0 0 0 0 3 2 4161 3 0 0 82,83,84,85,0,86,87,88,89,0,90,91,92,93,0,94,95,96,97,0,98,99,100,0 0 10 0 1283159360 0 0 0 0 3440 82 0 3441 83 0 3442 84 0 3443 85 0 3444 86 0 3445 87 0 3446 88 0 3447 89 0 3448 90 0 3449 91 0 3450 92 0 3451 93 0 3452 94 0 3453 95 0 3454 96 0 3455 97 0 3456 98 0 3457 99 0 3458 100 0 1037 828 0 11 829 quiz Test Yourself: Detecting a key press 0 0 1 1 0 0 1 2 4652015 0 0 1 3203,0 0 0 0 1283352140 0 0 0 0 3459 3203 0 1038 829 0 0 830 quiz Turns - test yourself 0 0 1 1 0 0 1 2 4652015 0 0 1 3195,3194,3196,3186,0 0 10 0 1266471836 0 0 0 0 3460 3194 0 3461 3195 0 3462 3196 0 3463 3186 0 1039 830 0 11 831 quiz Repeat self-test 0 0 1 1 0 0 1 2 4652015 0 0 1 3205,3206,3207,3208,0 4 10 0 1269309217 0 0 0 0 3464 3205 1 3465 3206 1 3466 3207 1 3467 3208 1 1040 831 0 11 832 quiz Which one goes faster? Try to answer this with out using Scratch! 0 0 1 1 0 0 1 2 4652015 0 0 1 3326,3327,0 2 10 0 1283331897 0 0 0 0 3468 3326 1 3469 3327 1 1041 832 0 11 833 quiz Increasing the tempo Try to answer these questions without using Scratch! 0 0 1 1 0 0 1 2 4652015 0 0 1 3328,3329,3330,3331,3332,0 5 10 0 1283331982 0 0 0 0 3470 3328 1 3471 3329 1 3472 3330 1 3473 3332 1 3474 3331 1 1042 833 0 11 834 quiz Non-numeric variables So far we've just been using variables to represent numbers, but they can also hold things like "Hello" or "Goodbye". We call these things <span style="font-style: italic;">strings</span>. And <span style="font-style: italic;">strings</span> can have a mixture of numbers and letters. Anything with at least 1 letter is a <span style="font-style: italic;">string</span>.<br /><br />So all of these are strings:<br /> <ul> <li>abcdef</li> <li>283838a</li> <li>a189181<br /></li> </ul> 0 0 1 1 0 0 1 2 4652015 0 0 1 3234,3235,3239,3236,3237,3238,0 6 10 0 1283332294 0 0 0 0 3475 3234 1 3476 3235 1 3477 3239 1 3478 3236 1 3479 3237 1 3480 3238 1 1043 834 0 11 835 quiz Changing Variables 0 0 1 1 0 0 1 2 4652015 0 0 1 3348,0 1 10 0 1283927305 0 0 0 0 3481 3348 1 1044 835 0 11 836 quiz If: What would you expect? This is not graded - see if you can predict what would happen! 0 0 1 1 0 0 1 2 4652015 0 0 1 3197,3198,3199,0 0 10 0 1283916881 0 0 0 0 3482 3199 0 3483 3197 0 3484 3198 0 1045 836 0 11 837 quiz Rock, Paper, Scissors: Choices 0 0 1 1 0 0 1 2 4652015 0 0 1 3200,3201,3202,0 3 10 0 1283919637 0 0 0 0 3485 3200 1 3486 3201 1 3487 3202 1 1046 837 0 11 838 quiz How was this made? 0 0 1 1 1 0 1 2 4652015 0 0 1 3240,3241,3242,0 3 10 0 1277999901 0 0 0 0 3488 3242 1 3489 3241 1 3490 3240 1 1047 838 0 11 839 quiz Don't use Script Variables Outside of their Script 0 0 1 1 0 0 1 2 4652015 0 0 1 3342,3343,3344,3345,0 4 10 0 1283353719 0 0 0 0 3491 3342 1 3492 3343 1 3493 3344 1 3494 3345 1 1048 839 0 11 840 quiz Changing regular variables with block variables 0 0 1 1 0 0 1 2 4652015 0 0 1 3232,0 1 10 0 1275581366 0 0 0 0 3495 3232 1 1049 840 0 11 841 quiz Change a regular variable within a block Try this self-test with your partner 0 0 1 1 0 0 1 2 4652015 0 0 1 3233,0 1 10 0 1275580982 0 0 0 0 3496 3233 1 1050 841 0 11 842 quiz Quiz: Weird Cases This quiz is not graded. By this point, we do not assume you know the answers to all of these questions, and we encourage you to make a best guess for each question. We also want to reinforce that the answers to these questions will be important later on, but that you can figure them out whenever you need to! The questions in this quiz are essentially <tt>what does this do</tt> questions. When dealing with these questions, you realize that people designed every programming language! So, people weighed pros and cons and made a decision about what the language should do in each situation. You might disagree with them about what should happen, but it is important to realize that you can always test to figure out what they decided, and that there is probably a reason behind their decision. 0 0 1 1 0 0 1 2 4652015 0 0 1 3215,3217,3218,3216,0 4 10 0 1284552326 0 0 0 0 3497 3217 1 3498 3215 1 3499 3218 1 3500 3216 1 1051 842 0 11 843 quiz Quiz: Loops and Lists This quiz is not graded. In this quiz, we will explore further how loops work with lists, and when precisely the condition of a <tt>repeat</tt> block is checked. 0 0 1 1 0 0 1 2 4652015 0 0 1 3347,3346,0 2 10 0 1284552311 0 0 0 0 3501 3347 1 3502 3346 1 1052 843 0 11 844 quiz Searching Through Time This quiz has only one question and is not graded. 0 0 1 1 0 0 1 2 4652015 0 0 1 3325,0 1 10 0 1285580063 0 0 0 0 3503 3325 1 1053 844 0 11 845 quiz Quiz If we run the following Scratch program and answer "yes", we note that finish is always 123. What are the possible values of finish if we answer "no"? (we've shown the definition of read and write finish with n) 0 0 1 1 0 0 1 2 4652015 0 0 1 0 10 0 1287004079 0 0 0 0 1054 845 0 11 846 quiz Different Trees Self Test Try to answer these without consulting Scratch BYOB 0 0 1 1 0 0 1 2 4652015 0 0 0 3219,3220,3221,0 3 10 0 1275019209 0 0 0 0 3504 3219 1 3505 3220 1 3506 3221 1 1055 846 0 11 847 quiz Different Versions of Tree This is a self-test. 0 0 1 1 0 0 1 2 4652015 0 0 1 3222,3223,0 2 10 0 1275020908 0 0 0 0 3507 3222 1 3508 3223 1 1056 847 0 11 848 quiz What was changed? 0 0 1 1 0 0 1 2 4652015 0 0 1 3226,3224,3228,3227,3225,0 5 10 0 1275022378 0 0 0 0 3509 3224 1 3510 3226 1 3511 3225 1 3512 3227 1 3513 3228 1 1057 848 0 11 849 quiz Where is the base case? answer this self-test with your partner 0 0 1 1 0 0 1 2 4652015 0 0 1 3229,0 1 10 0 1275333842 0 0 0 0 3514 3229 1 1058 849 0 11 850 quiz Tracing Code on Paper Do this self-test with your partner 0 0 1 1 0 0 1 2 4652015 0 0 1 3230,0 1 10 0 1275335054 0 0 0 0 3515 3230 1 1059 850 0 11 851 quiz Considering Exceptional Cases in the Range Function Do this self-test with your partner after you have written the function from the previous step. 0 0 1 1 0 0 1 2 4652015 0 0 1 3231,0 1 10 0 1275336668 0 0 0 0 3516 3231 1 1060 851 0 11 852 quiz Simulation today This quiz will test your comprehension of the applications of computer simulations to other fields. The answers will not be directly available from the reading, but should be deducible from the information provided in it. 0 0 1 1 0 0 1 2 4652015 0 0 1 3243,0 1 10 0 1282532223 0 0 0 0 3517 3243 1 1061 852 0 11 853 quiz Quick Review What does BYOB return as the value for each of the following blocks?<br /><br />For your answers:<br /> <ul> <li>If the block returns a list, type in each of the elements with a space in between. IE if the list is "[4] [5] [6]", type in "4 5 6" (without quotes) as your answer.</li> <li>If the block returns a empty list, then just type in "blank" (without quotes) as your answer.<br /></li> <li>If the block returns "true" or "false", type in "true" or "false" (without the quotes) as your answer. </ul> <em>Try to answer these questions without using BYOB.</em> Ask questions if any specific example(s) is confusing. 0 0 1 1 0 0 1 2 4652015 0 0 1 3333,3334,3335,3336,3337,3338,0 6 6 0 1288629522 0 0 0 0 3518 3334 1 3519 3335 1 3520 3336 1 3521 3337 1 3522 3338 1 3523 3333 1 1062 853 0 7 854 quiz Quick Review 2 0 0 1 1 0 0 1 2 4652015 0 0 1 3340,0 1 10 0 1283140518 0 0 0 0 3524 3340 1 1063 854 0 11 855 quiz What kind of pattern was alpha? From 10 miles up, what kind of pattern was that entire MapReduce operation? (answer at the end) mapping finding counting filtering testing combining 0 0 1 1 0 0 1 2 4652015 0 0 1 0 10 0 1294865682 0 0 0 0 1064 855 0 11 856 quiz What kind of pattern was Love? From 10 miles up, what kind of pattern was that entire MapReduce operation? (answer at the end) mapping finding counting filtering testing combining 0 0 1 1 0 0 1 2 4652015 0 0 1 0 10 0 1294865754 0 0 0 0 1065 856 0 11 3954 resource Welcome to Scratch html

<h1>Welcome to Scratch</h1> Let's open up Scratch! You will see a screen like the one shown below. Explore the aspects of the user interface highlighted in red. <br /> Play around for a while and see if you can figure out the major components of the interface. In the next step, you will make your first project and explore further. <br /><br /> <div style="text-align: center;"><img hspace="0" border="0" vspace="0" style="width: 756px; height: 505px;" title="Screenshot of Scratch" alt="Screenshot of Scratch" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab01$@SLASH@$Screenshot.jpg" /></div> <br /><br /> 1283126247 3955 resource Make a Sprite sing! html

<h1>Make a Sprite sing!</h1> For your first project, make a quick song! You will find the following <strong>blocks</strong> in the <tt>Sound</tt> tab useful; feel free to change the default numbers as you see fit: <br /> <div style="text-align: center;"><img hspace="0" height="419" border="0" width="220" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab01$@SLASH@$Sounds.jpg" alt="Sounds" title="Sounds" /></div> <br /> While you are working on it, try to figure out how to connect and disconnect blocks, and how to remove a piece from inside a long script. Also, what do you think is the difference between these two blocks? <br /><br /> <div style="text-align: center;"><img src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab01$@SLASH@$PlaySoundMeow.jpg" alt="Play Sound Meow" title="Play Sound Meow" /> and <img src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab01$@SLASH@$PlaySoundMeowUntilDone.jpg" alt="Play Sound Meow Until Done" title="Play Sound Meow Until Done" /></div> <br /> <em>Hint</em>: Try to use many copies of one of the blocks in a row, and hear the result. Do this for each block. 1283159315 3956 resource Some Starting Scratch Lingo html

<h1>Some Starting Scratch Lingo</h1> As we explore Scratch and as we learn new ideas in computer science, you will be seeing a few words and terms that you may not understand. We will always try to define new vocabulary in our <tt>Lingo List</tt>. Below, we show some terms that we will use for the various items in Scratch. Keep thinking of more as the class continues! <br /><br /> <h2>Scratch Lingo</h2> <table rules="rows" frame="void" width="60%" border="2" style="border-style: none; background-image: none; float: none; text-align: left; vertical-align: top;"> <tbody> <tr> <td width="50%" valign="top"><strong>Tabs</strong> (for blocks)<br /> </td> <td width="50%" valign="top"><img hspace="0" height="118" width="217" vspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab01$@SLASH@$Tabs.jpg" alt="Tabs (for blocks)" title="Tabs (for blocks)" /><br /> </td> </tr> <tr> <td style="vertical-align: top;"><strong>Tabs</strong> (per sprite) </td> <td style="vertical-align: top;"><img hspace="0" height="28" width="233" vspace="0" border="0" title="Tabs (per sprite)" alt="Tabs (per sprite)" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab01$@SLASH@$Tabs2.jpg" /><br /> </td> </tr> <tr> <td style="vertical-align: top;"><strong>Blocks</strong> </td> <td style="vertical-align: top;"><img hspace="0" height="222" width="232" vspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab01$@SLASH@$Blocks.jpg" alt="Blocks" title="Blocks" /><br /> </td> </tr> <tr> <td style="vertical-align: top;"><strong>Script</strong> </td> <td style="vertical-align: top;"><img hspace="0" height="97" width="216" vspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab01$@SLASH@$Script.jpg" alt="Script" title="Script" /><br /> </td> </tr> <tr> <td style="vertical-align: top;"><strong>Sprite</strong> </td> <td style="vertical-align: top;"><img hspace="0" height="149" width="115" vspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab01$@SLASH@$Sprite.jpg" alt="Sprite" title="Sprite" /> and <img hspace="0" height="73" width="66" vspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab01$@SLASH@$Spriter.jpg" alt="Sprite 2" title="Sprite 2" /><br /> </td> </tr> <tr> <td style="vertical-align: top;"><strong>Costume</strong><br />(Each sprite can have multiple costumes.)<br /> </td> <td style="vertical-align: top;"><img hspace="0" height="320" width="314" vspace="0" border="0" title="There should be an image here" alt="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab01$@SLASH@$Costumes.jpg" /><br /> </td> </tr> <tr> <td style="vertical-align: top;"><strong>Stage</strong> </td> <td style="vertical-align: top;"><img hspace="0" vspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab01$@SLASH@$Stage.jpg" alt="Stage" title="Stage" style="width: 306px; height: 251px;" /><br /> </td> </tr></tbody> </table> <h2>More Computer Science Lingo</h2> <table rules="rows" frame="void" width="60%" border="2" style="border-style: none; background-image: none; float: none; text-align: left; vertical-align: top;"> <tbody> <tr> <td width="50%" valign="top" style="color: rgb(0, 0, 0); text-align: left;"><strong>Bug</strong> </td> <td width="50%" valign="top" style="color: rgb(0, 0, 0);"><span style="color: rgb(0, 0, 0);">A defect (or a problem) in the code or routine of a program.</span> </td> </tr> <tr> <td width="50%" valign="top" style="color: rgb(0, 0, 0);"><strong>User Interface</strong> </td> <td width="50%" valign="top" style="color: rgb(0, 0, 0);"><span style="color: rgb(0, 0, 0);">The place where interaction between humans and machines occurs. For example, Windows, Scratch, the iPod touch screen, and even your keyboard are examples of user interfaces!</span> </td> </tr> </tbody> </table></span> 1283129228 3957 resource Experiment with a short Scratch play html

<h1>Experiment with a short Scratch play</h1> <h2>Scripts</h2> Try to make these scripts in Scratch! You will find that the Cat and the Duck have completely separate script areas. Click on each character to see their script area. Once you are done, press the green flag to start the short play. <br /><br /> <div style="margin-left: 40px;"><img hspace="0" height="" border="0" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab01$@SLASH@$CatPlayScript.jpg" alt="Script of the Cat for the Play" title="Script of the Cat for the Play" /> <img hspace="0" height="" border="0" vspace="0" title="Script of the Duck for the Play" alt="Script of the Duck for the Play" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab01$@SLASH@$DuckPlayScript.jpg" /><br /></div><br /> A note about style: You will notice that we chose to name the messages that were broadcast so that it would help us keep track of what we were doing and what messages we were sending. We recommend that you do this in your projects! <h2>Hints</h2> <ol> <li> To choose a new sprite from a library of existing sprites, click on the icon below the stage that looks like a folder. <br /> <div style="margin-left: 40px;"><img hspace="0" height="443" border="0" width="497" vspace="0" title="New Sprite" alt="New Sprite" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab01$@SLASH@$NewSprite.jpg" /></div> </li> <br /><br /> <li>Try to figure out what the commands (whose images are on the left) and buttons (whose images are on the right) do. These will be helpful to get the characters to face each other. <br /> <img hspace="0" height="102" border="0" width="146" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab01$@SLASH@$TurnCommands.jpg" alt="Turn Commands" title="Turn Commands" /> <img hspace="0" height="95" border="0" width="318" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab01$@SLASH@$TurnButtons.jpg" alt="Turn Buttons" title="Turn Buttons" /> <br /> </ol> <h2>Exercise</h2> Once you have this working, change the script of the "play" so that each character says an additional line. <br /> 1283157240 3958 resource Single Step Mode html

<h1>Single Step Mode</h1> It can be helpful to see which block is executing at each time. Click <tt>Edit</tt> and then <tt>Start Single Stepping</tt> to highlight the block that is executing when you run the scripts. <br /><br /> <div style="margin-left: 80px;"><img hspace="0" height="162" border="0" width="251" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab01$@SLASH@$Wait$@SLASH@$SingleStep.jpg" alt="SingleStep" title="SingleStep" /></div> Once you are done, click <tt>Edit</tt> and then <tt>Stop Single Stepping</tt> to stop the single-stepping process. 1283129408 3959 resource Exporting Sprites html

<h1>Exporting Sprites</h1> By this point, you have probably figured out how to save your Scratch projects, but you can also save individual Sprites separately. <br /><br /> To <strong>save</strong> (or <strong>export</strong>) a Sprite, right-click on the sprite and select <tt>export this sprite</tt>. To <strong>load</strong> (or <strong>import</strong>) a Sprite, click on the icon with a folder next to <tt>New Sprite</tt> (circled in yellow in the image below) and select the Sprite that you want to add to your project. <br /> <div style="text-align: center;"><img hspace="0" height="185" border="0" width="263" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab01$@SLASH@$ExportSprite.jpg" alt="Export Sprite" title="Export Sprite" /></div> 1283131974 3960 resource Homework: Get Familiar with Scratch html

<h1>Homework: Get Familiar With Scratch</h1> The main idea behind this homework is to get more comfortable with Scratch, so play around and try new things! Be sure to make a note if there is anything that seems confusing, and ask your lab TA or lab assistants about it later. <h2>Activities</h2> <ol> <li>Finish up any of the lab sections that you did not finish.</li> <li>Take the survey a few sections later.</li> <li>Set up Scratch on your home computer, so that you can work at home. You can download Scratch from <a href="http://scratch.mit.edu" target="_blank">http://scratch.mit.edu</a>.</li> <li>Look at the <a href="http://scratch.mit.edu/channel/featured" target="_blank">galleries of projects</a> on the <a href="http://scratch.mit.edu" target="_blank">Scratch</a> website.</li> <li>Create a Scratch account to be able to post your Scratch projects online at <a href="http://scratch.mit.edu/" target="_blank">http://scratch.mit.edu</a>.</li> <li>Download a project from the Scratch projects website. Modify something and submit it.</li> <li>Make a movie or a play to show off during the next lab and submit it. In general, your movie should have at least:</li> <ul> <li>One block that we did not use during lab.</li> <li>Two characters.</li> <li>Ten total broadcasts of a couple of messages.</li> </ul> Give the file a name based on the movie or the play, followed by your name. So, for example, if John Doe made the play involving the Cat and the Duck, the file would be named "Cat-Duck-John-Doe". </ol> <h2>Submission</h2> The <span style="font-style: italic;">original</span> and <span style="font-style: italic;">modified</span> Scratch project, as well as the movie or play, are due as deliverables for this assignment<strong></strong>. You will turn in your work on <a href="http://bspace.berkeley.edu">bSpace</a>. When you log in to bSpace, go to the <tt>Assignments</tt> tab, and click on <tt>Homework 01</tt>. There, you will upload your work and hit <tt>Submit</tt> to turn in your work. 1296603448 3961 resource Optional: Musical Magic html

<h1>Optional: Musical Magic</h1> In the lab today, you made a simple song, but let's push that to the extreme and really make music! <br /><br /> Alex Ruthmann, a professor of music at the University of Massachusetts Lowell has posted some amazing music projects <a target="_blank" href="http://scratch.mit.edu/users/alexruthmann">here</a>. He uses a technique whereby he stores the notes to be played in a list, so that he can set the musical scale that he will be using. We have not worked with lists yet, but we will be working with them a lot in the future, and the practice can't hurt. <br /> 1283159096 3962 resource Optional: Electric Keyboard html

<h1>Optional: Electric Keyboard</h1> <h2>Activity</h2> Try to make an electric keyboard! The code below shows a start: <br /><br /> <img hspace="0" height="289" width="190" vspace="0" border="0" title="Starting to code an Electric Keyboard" alt="Starting to code an Electric Keyboard" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab01$@SLASH@$ElectricKeyboard.jpg" /> <h2>Hint</h2> You might want to print or draw a piano keyboard or a computer keyboard to keep track of how you have mapped keys to notes. We have provided a few images below that you can print out to work with. <br /><br /> <img hspace="0" vspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab01$@SLASH@$Keyboard.jpg" alt="Keyboard" title="Keyboard" style="width: 605px; height: 147px;" /> <br /><br /> <img hspace="0" vspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab01$@SLASH@$CompKeyboard.jpg" alt="Computer Keyboard" title="Computer Keyboard" style="width: 637px; height: 246px;" /> <h2>Challenge</h2> Add additional functionality, perhaps by adding scripts for other keys on the computer keyboard, so that your electric keyboard can change: <br /> <ul> <li>Volume,</li> <li>Instrument, and/or</li> <li>Tempo.</li> </ul> 1283159079 3963 resource Moving with the Arrow Keys html

<h1>Moving with the Arrow Keys</h1> Often, we will want to move the character with the arrow keys (i.e. up, down, left, and right). We can use the piece <tt>point in direction</tt> as shown below. <br /> <div style="text-align: center;"><img hspace="0" height="478" border="0" width="580" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab03$@SLASH@$PointInDirection.jpg" alt="Point in direction" title="Point in direction" /> <br /></div> <br /> There are still a few things in the Scratch user interface that you probably have not used yet. Experiment with the rotation controls shown below and make sure you understand the behavior of each. These will probably come in handy at some point! <br /><br /> <div style="text-align: center;"><img hspace="0" height="93" border="0" width="266" vspace="0" title="Rotation Controls" alt="Rotation Controls" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab03$@SLASH@$RotationControls.jpg" /> <br /></div> <br /> Finally, make a character move around based upon the keys that you have pressed. You will need to use one of the rounded "top block" pieces, such as in the example shown below. These can respond to key presses and start a script. <br /><br /> <div style="text-align: center;"><img hspace="0" height="78" border="0" width="200" vspace="0" title="Top Piece" alt="Top Piece" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab03$@SLASH@$UpArrow.jpg" /><br /></div> 1283350848 3964 resource Two characters running! html

<h1>Two characters running!</h1> We are going to make a small game of tag in Scratch. Make a second character that is controlled by a different set of keys. <br /><br /> <div style="text-align: center;"><img hspace="0" height="147" border="0" width="233" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$TagGame$@SLASH@$RenamedSprites2.jpg" alt="Two sprites that have been renamed" title="Two sprites that have been renamed" /><br /></div> <br /> We want to be able to refer to our characters with intuitive names. By default, your sprites will probably be called things like <tt>Sprite1</tt> and <tt>Sprite2</tt>. Rename them by clicking on the sprite and typing into the text box at the top of the screen, as shown below: <br /><br /> <div style="text-align: center;"><img hspace="0" height="97" border="0" width="273" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$TagGame$@SLASH@$CatRenamed.jpg" alt="Cat renamed" title="Cat renamed" /><br /></div> 1283351585 3965 resource Game of TAG! html

<h1>Game of TAG!</h1> <br /> We want one of the characters to react if the two characters touch. In the last step, we showed an example with <tt>Cat</tt> and <tt>Mouse</tt>. We can add either of the following equivalent scripts to the <tt>Mouse</tt> sprite to say <tt>OH NOs!!!</tt> when it touches the cat. <br /><br /> <div style="text-align: center;"><img hspace="0" height="139" border="0" width="252" vspace="0" title="Mouse script when touching cat" alt="Mouse script when touching cat" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$TagGame$@SLASH@$Script.jpg" /> <br /> or <br /> <img hspace="0" height="179" border="0" width="244" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$TagGame$@SLASH@$Script3.jpg" alt="Mouse script when touching cat (with embedded 'if')" title="Mouse script when touching cat (with embedded 'if')" /><br /></div> <br /><em>Note</em>: One really important thing to note here is that once we click the green flag, the scripts above will <strong>always</strong> be running: notice that they always have a white outline. Compare this to the script below that would only run once when you click the green flag. The functionality above is often called an <strong>infinite loop</strong>, and can be very helpful when we want something to continue running forever. <br /><br /> <div style="text-align: center;"><img hspace="0" height="141" border="0" width="254" vspace="0" title="Script with only IF" alt="Script with only IF" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$TagGame$@SLASH@$Script2.jpg" /><br /></div></div> 1283351682 3966 resource Experiment with drawing commands html

<h1>Experiment with drawing commands</h1> Try to get comfortable with the pieces shown below. Figure out what each one does and try to use these pieces to draw a square or a simple picture. <br /><br /> <div style="margin-left: 200px;"><img hspace="0" height="180" border="0" width="130" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab01$@SLASH@$MovePieces.gif" alt="Move Pieces Image" title="Move Pieces Image" /><br /></div> <div style="text-align: left;">Note <br /> <ul> <li>You probably want to make your character smaller so that it is easier to see where it is drawing. HINT: Check out the blocks under the "Looks" tab. </li> <li>Make sure that you click on the menu option in the image below so that the character displays rotations.<br /></li> </ul><img hspace="0" height="129" border="0" width="447" vspace="0" title="There should be image here" alt="There should be image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$Drawing_tips$@SLASH@$ShowRotations.jpg" /><br /> <ul> <li>You also will want to show the direction and x and y position of the character. In the Motion tab you can select for these to be shown on the stage (like below). <br /></li> <ul> <li>Try it - Does the turn command change the x or y position? <br /></li> </ul> </ul> <div style="margin-left: 40px;"><img hspace="0" height="751" border="0" width="207" vspace="0" title="There should be image here" alt="There should be image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$Drawing_tips$@SLASH@$X-POsition.jpg" /><img hspace="0" height="406" border="0" width="497" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$Drawing_tips$@SLASH@$PositionsDisplayed.jpg" alt="There should be image here" title="There should be image here" /></div> </div> 1295855450 3967 resource Experiment with Repeat html

<h1>Experiment with Repeat</h1>We can use a <span style="font-family: courier new,courier,monospace;">Repeat </span>to make drawing shapes a lot easier! You can see below a script to draw a square. <br /> <br /> <div style="margin-left: 120px;"><img hspace="0" height="97" border="0" width="142" vspace="0" title="Square example image" alt="Square example image" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab01$@SLASH@$SquareExample.gif" /><br /></div> <br /> Using a <span style="font-family: courier new,courier,monospace;">Repeat </span>try to draw the following shapes: <br /> <ul> <li>Equilateral Triangle</li> <li>Pentagon</li> <li>Hexagon</li> <li>Octagon</li> <li>Circle<br /></li> <li>Five-sided Star</li> </ul>Save the scripts as you go because next you'll be trying to figure out a pattern!<br /> 1284921893 3968 resource Tempo html

<h3>Tempo</h3> <p>But it doesn't have to be so difficult to change the speed of a song! We can keep track of a variable that we will call "tempo" that will change how long 1 beat is. </p> <p>In the sounds tab find the tempo block and select the check box next to "tempo" so that you can see the value of the variable "tempo" on the stage.</p> <div style="margin-left: 80px;"> <p><img hspace="0" height="93" border="0" width="162" vspace="0" title="tempo blocks" alt="tempo blocks" src="$@FILEPHP@$$@SLASH@$ATDP$@SLASH@$Lab_2$@SLASH@$tempoBlocks.jpg" /> <img hspace="0" height="70" border="0" width="211" vspace="0" title="tempo variable" alt="tempo variable" src="$@FILEPHP@$$@SLASH@$ATDP$@SLASH@$Lab_2$@SLASH@$tempo_visible.jpg" /></p></div> <p>Now double-click on the tempo blocks and see how the variable tempo changes!</p> <p>Make a song and change the tempo.. <br /></p> 1282935524 3969 resource Change how fast the tempo changes html

<h3>Change how fast the tempo changes</h3>In the quiz we saw something that increased the tempo. There are three main parts of the script:<br /> <ol> <li>Initialize the value of "tempo"</li> <li>Inside the repeat - <ul> <li>Use the value of "tempo"</li> <li>Change the value of "tempo" <br /></li> </ul> </li> </ol> <br /> <div style="margin-left: 40px;"><img hspace="0" border="0" vspace="0" src="$@FILEPHP@$$@SLASH@$ATDP$@SLASH@$Lab_2$@SLASH@$drumTempo_repeat4.gif" alt="incrasing tempo" title="incrasing tempo" style="width: 342px; height: 166px;" /><br /></div><br />Try It!<br /> <div style="margin-left: 40px;"> <ul> <li>Make this script in Scratch. </li> <li>Make another version where the tempo increases faster!</li> <li>Make another version where the tempo increases much-slower!</li> <li>Make another version where the tempo starts out fast and then decreases!</li> <li>Make another version where the tempo starts out slow, then gets fast, then gets slow again. <br /></li> </ul><br /></div> 1282941149 3970 resource Variable Tutorial (Scales) html

<h3>Variable Tutorial (Scales)</h3>The goal of this tutorial is to make script that plays a scale! <br /><br />The variable "tempo" was made for us. We're going to make our own variable now!<br /><br /> <ul> <li>Click on the variables tab and click "Make a variable"<br /></li> </ul> <div style="text-align: center;"><img hspace="0" height="253" border="0" width="216" vspace="0" title="tutorial image" alt="tutorial image" src="$@FILEPHP@$$@SLASH@$ATDP$@SLASH@$Lab_2$@SLASH@$variables$@SLASH@$Variables.jpg" /><br /></div> <ul> <li>In the box that pops up - type the name of our variable "my note" (don't type the quotes).<br /></li> </ul> <div style="text-align: center;"><img hspace="0" height="189" border="0" width="311" vspace="0" title="tutorial image" alt="tutorial image" src="$@FILEPHP@$$@SLASH@$ATDP$@SLASH@$Lab_2$@SLASH@$variables$@SLASH@$my_note_variable.jpg" /><br /></div> <ul> <li>Now you'll have blocks to use for your variable (just like we had blocks to use for tempo). <br /></li> </ul> <div style="text-align: center;"><img hspace="0" height="404" border="0" width="223" vspace="0" title="tutorial image" alt="tutorial image" src="$@FILEPHP@$$@SLASH@$ATDP$@SLASH@$Lab_2$@SLASH@$variables$@SLASH@$VariableAvailable.jpg" /><br /></div><br /> <ul> <li>Make the block on the right using your variable "my note". Hint - look how similar it is to the repeat that changed tempo! It has the same 3 important pieces:</li> </ul> <ol> <li>Initialize the value of "my note"</li> <li>Inside the repeat - <ul> <li>Use the value of "my note"</li> <li>Change the value of "my note" <br /></li> </ul> </li> </ol> <br /> <div style="text-align: center;"><img hspace="0" height="102" border="0" width="444" vspace="0" title="Loops" alt="Loops" src="$@FILEPHP@$$@SLASH@$ATDP$@SLASH@$Lab_2$@SLASH@$comparisonofLoops.gif" /><br /></div><br /> <ul> <li>Make a script that plays every other note from 50-100. <br /></li> </ul> 1282941655 3971 resource Common Bug - Set vs. Change html

<h3>Common Bug - Set vs. Change</h3><br />A very common mistake is to use a change block when you need a set block or use a set block when you need a change block. <br /><br />It is actually a little more complicated, in that you can make your set block act like a change block. <br /><br /> <div style="margin-left: 80px;"><img hspace="0" height="156" border="0" width="214" vspace="0" title="Set versus Change" alt="Set versus Change" src="$@FILEPHP@$$@SLASH@$ATDP$@SLASH@$Lab_2$@SLASH@$set_versus_change.gif" /><br /></div><br /><br />Figure out what could be put in the blank below to make a change block act like a set block! <br /><br /> <div style="margin-left: 80px;"><img hspace="0" height="28" border="0" width="310" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$setWithAChange.gif" alt="Set with a Change" title="Set with a Change" /><br /></div><br /> 1282942508 3972 resource Variable Sized Shapes html

<h3>Variable Sized Shapes</h3><br />We want you to combine what you've learned about variables and shapes to fill in the blank below.<br /> <ul> <li>The program should draw a shape with a different number of sides based upon the value of a variable. For example, if the variable <span style="font-family: courier new,courier,monospace;">sides </span>was 3, it would draw a triangle, if it was 8, it would draw an octagon.</li> </ul> <div style="text-align: center;"><img hspace="0" height="161" border="0" width="204" vspace="0" title="There should be an image here" alt="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$variableShapes.jpg" /><br /> </div> 1278024661 3973 resource Countdown html

<h3>Countdown</h3>Make a character count down from 10 by using a variable named <img hspace="0" height="20" border="0" width="106" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$Countdown$@SLASH@$CurrentNumberVariable.jpg" alt="current number" title="current number" />. Hint you'll need to use a <span style="font-family: courier new,courier,monospace;">REPEAT</span><br /> <div style="text-align: center;"> <img hspace="0" height="203" border="0" width="273" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$Countdown$@SLASH@$CountDown.jpg" alt="Conntdown" title="Conntdown" /><br /></div><br />We can use any of the following commands to decrease the value of <img hspace="0" height="20" border="0" width="106" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$Countdown$@SLASH@$CurrentNumberVariable.jpg" alt="current number" title="current number" />.<br /><br /> <div style="text-align: center;"><img hspace="0" height="117" border="0" width="296" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$Countdown$@SLASH@$CurrentNumber_methods.gif" alt="blocks to modify current number " title="blocks to modify current number " /><br /> </div> 1295855552 3974 resource Repeat Until html

<h3>Repeat Until</h3>There is another Scratch piece that lets us repeat things. It is called "repeat until". Just like REPEAT, it will do everything inside the C-shaped block a certain number of times. Except, before it starts the loop each time, it checks to see if the condition (below x > 5) is true. If this is condition is true, then it will not repeat again. <br /><br /> <div style="margin-left: 40px;"><img hspace="0" height="131" border="0" width="161" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$Repeat_Until$@SLASH@$whileLoop_simple.gif" alt="There should be an image here " title="There should be an image here "><br /></img><br /></div><br />It can be really helpful to keep track of what the variable X is at each point to help us understand how this new piece works. <br /> <ul> <li>In the right column we keep track of the value of x. </li> <li>In the diagram below we draw a horizontal line every time we start the loop. <br /></li> <ul> <li>Here we labeled each line "Top of loop" and "Bottom of loop" but we could just use the horizontal line to keep track of this information. <br /> </li> </ul> <li>Within each loop the variable x increases by 1, so we write down the new value for x.</li> </ul> <div style="margin-left: 40px;"><img hspace="0" height="571" border="0" width="388" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$Repeat_Until$@SLASH@$TrackingVariables.jpg" alt="There should be an image here" title="There should be an image here" /><br /></div>Try to use a chart like the one above to keep track of what happens in the complicated "repeat until" code below. <br /><br /> <div style="margin-left: 40px;"><img hspace="0" height="215" border="0" width="168" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$Repeat_Until$@SLASH@$whileLoop.gif" alt="There should be an image here" title="There should be an image here" /><br /></div> 1277820221 3975 resource Draw a Squiral html

<h3>Draw a Squiral<br /></h3>Make a new variable <span style="font-family: courier new,courier,monospace;">Length</span>. Draw the "Squiral" (Square+Spiral) below. If you need a hint, go back to this previous step: <a href="$@RESOURCEVIEWBYID*8756@$">HERE</a>.<br /> <div style="margin-left: 40px;"><img hspace="0" height="215" border="0" width="213" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab01$@SLASH@$LengthVariable.jpg" alt="Length Variable" title="Length Variable" /> <img hspace="0" height="263" border="0" width="250" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab01$@SLASH@$Squiral.jpg" alt="Squiral" title="Squiral" /><br /></div><br /> 1282943049 3976 resource Homework: Countdown with Sprites html

<h1>Homework: Countdown with Sprites</h1> Often, we want to display text or numbers on the screen without using the <tt>say</tt> block. We have written a program that displays one number based upon a variable named <tt>digit</tt>. You can download the program <a title="Digital display" href="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$DigitalDisplay.sb">here</a>. You should modify this program to work for five digits! (Initially, however, you may want to start by modifying it just to work with two digits.) <h2>How does the original code work?</h2> We have created a <tt>MyDigit</tt> sprite with ten different costumes, one for each digit, as shown below. Costume 1 corresponds to the digit <tt>1</tt>, costume 2 corresponds to the digit <tt>2</tt> and so on. Costume 10 corresponds to the digit <tt>0</tt>. Each costume has a name (for example, <tt>one</tt>, as shown circled in yellow) and a number (for example, <tt>1</tt>, as shown circled in red). <br /><br /> <div style="text-align: center;"><img border="0" width="351" vspace="0" hspace="0" height="739" title="Digital display" alt="Digital display" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$Score_Display$@SLASH@$Costumes.jpg" /> <br /></div><br /> When we use the <tt>switch to costume</tt> block, we can specify either the name or the costume number. In the script below, we use the costume number (1-9) to set the costume unless the digit is 0. If the digit is 0, we cannot just tell it to switch to costume 0 (because there is no costume 0), so we have to use the name of the costume (<tt>zero</tt>). <div style="text-align: center;"><img border="0" width="194" vspace="0" hspace="0" height="142" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$Score_Display$@SLASH@$DigitDisplay.gif" alt="Example script using 'switch to costume'" title="Example script using 'switch to costume'" /></div> <br /><em>Hint</em>: You may find the <img border="0" width="72" vspace="0" hspace="0" height="25" title="'Mod' block" alt="'Mod' block" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$Score_Display$@SLASH@$modImage.jpg" />block helpful. To figure out what it does, right-click on the block and select <tt>Help</tt>.<br /><br />Here's a sample of how the countdown timer should work when it starts at 24:<br /> <div style="text-align: center;"> <object width="640" height="385"><param name="movie" value="http://www.youtube.com/v/7m33R_YRh3Q?fs=1&hl=en_US" /><param name="allowFullScreen" value="true" /><param name="allowscriptaccess" value="always" /><embed width="640" height="385" src="http://www.youtube.com/v/7m33R_YRh3Q?fs=1&hl=en_US" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" /> </object></div> <h2>Upload and Submit</h2> Once you are done, go to the <a href="http://bspace.berkeley.edu">bSpace</a> site and into the <tt>Assignments</tt> tab. Click on <tt>Homework 02</tt> and upload your Scratch solution. Once you also upload your drawing for the next section (<tt>Draw a Picture in Scratch</tt>), press <tt>Submit</tt>. 1296602911 3977 resource Homework: Draw a Picture in Scratch html

<h1>Homework: Draw a Beautiful Picture in Scratch</h1> Create something (anything!) beautiful with the drawing tools in Scratch. For instance, we made the following image in Scratch: <br /><br /> <div style="text-align: center;"><img border="0" width="499" vspace="0" hspace="0" height="401" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$Flower.jpg" alt="Flower" title="Flower" /></div> <br /><br /> The image above plays around with pen color and pen size. If you want to create more complex images, you probably want to use broadcasts to delegate the drawing of different parts of the image. For example, we used the following broadcasts for the image above: <br /><br /> <div style="text-align: center;"><img border="0" width="205" vspace="0" hspace="0" height="209" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$Broadcast_messages_for_flower.gif" alt="Broadcast messages for flower" title="Broadcast messages for flower" /></div> <br /><br /> Once we get all of your submissions, we will create a quilt that we will decorate the lab with! <br /><br /> <em>Tip</em>: Your images will draw more quickly if you use <img border="0" width="47" vspace="0" hspace="0" height="32" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$Hide.jpg" alt="Hide" title="Hide" />to hide the character. <h2>Submission Instructions</h2> In order to submit your picture, you will need to take a <strong>screen capture</strong>, which is basically a picture of what your computer screen looks like. <h3>What kind of a computer do you have?</h3> If you are on a computer with Microsoft Windows, use <a href="http://graphicssoft.about.com/cs/general/ht/winscreenshot.htm">these</a> instructions to create a screen capture. If you are on a computer with Macintosh (such as the lab computers), use <a href="http://graphicssoft.about.com/od/screencapturemac/ht/macscreenshot.htm">these</a> instructions instead (you only need step 1). Give the file a name based on the image, followed by your name. So, for example, if John Doe drew the flower above, the file would be named "Flower-John-Doe". <h3>Upload and submit</h3> Once you are done, go to the <a href="http://bspace.berkeley.edu">bSpace</a> site and into the <tt>Assignments</tt> tab. Click on <tt>Homework 02</tt> and upload your picture. If you have also uploaded your solution to the previous section (<tt>Countdown with Sprites</tt>), press <tt>Submit</tt>. 1296603395 3978 resource Homework: Survey #2 (due Friday) file http://www.surveymonkey.com/s/DGCGDQX

This is the second (and last for a while!) survey that we will be asking you to complete. Since CS10 is a new course, this is very important to us to gauge the value of the course to you as a student. Please take the time to answer the questions as accurately as possible. Thanks!!

1283367629 3979 resource Reviewing Variables html

<h1>Working with variables</h1> Last class's lab was aimed at getting you comfortable with using <strong>variables</strong> to store values and thus to do things you couldn't do before. Variables are one of the central concepts in computer science and one of the most powerful tools in a programmer's toolbox. They will pop up steadily throughout the rest of the semester. <br /><br /> These are two blocks that we will be seeing a <em>lot</em> in the coming months. Make sure that you are clear with the differences between them. <br /><br /> <img hspace="0" height="139" border="0" width="422" vspace="0" title="Set and change" alt="Set and change" src="$@FILEPHP@$$@SLASH@$set_change.png" /> <br /><br /> As we mentioned in the last lab, you can use these two blocks to accomplish the same thing, but it probably makes more sense to use one over the other depending on what you are trying to do. <strong>If you are trying to set the value relative to what it already is</strong> (such as adding $5 to a variable storing a bank balance), you will probably be better off using a <tt>change</tt> block. <strong>If you are trying to set it to a totally new, unrelated value</strong> (such as resetting someone's score in a video game), then you will probably want to use a <tt>set</tt> block. 1295855985 3980 resource How many days are there in a given month? html

<h1>How many days are there in a given month?</h1> We have created <a href="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$DaysInMonth.sb" title="DaysInMonth Scratch File">a Scratch file</a> that calculates the number of days in a month based on a number that a user types in; the number represents the month. Discuss with your partner how this Scratch file works. There are a lot of new things in this program that you may not have seen before, so be sure to play around with them. <br /><br /> <img hspace="0" height="284" border="0" width="884" vspace="0" title="DaysInMonth Script" alt="DaysInMonth Script" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab03$@SLASH@$DaysInMonth2.gif" /> <br /><br /> <em>Note</em>: This code is not written with the best style. We hope your reaction to this is <em>YUCK</em>! We have made the code explicitly complex to help you review some of the blocks from the first lab. In future lab sessions, we will learn of different ways to write this code more elegantly. 1283917297 3981 resource Random Character html

<h1>Random Character</h1> We can generate a random number in Scratch between any two numbers (inclusive) using the <tt>random</tt> block: <br /><br /> <div style="text-align: center;"> <img hspace="0" height="31" border="0" width="153" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab03$@SLASH@$Random.jpg" alt="Random" title="Random" /> </div> <br /> This block (with the round edges) is a <strong>reporter</strong> block -- it <em>reports</em> a value. We can use this block inside other blocks that take a value: <br /><br /> <div style="text-align: center;"> <img hspace="0" height="243" border="0" width="301" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab03$@SLASH@$RandomEverywhere.gif" alt="Random Everywhere" title="Random Everywhere" /> </div> <br /><br /> Try the following out: <ul> <li>Make a character move around the screen randomly.</li> <li>Now, make your character move around randomly, but still stay within 100 pixels (in the <tt>x</tt>- and <tt>y</tt>- directions) of the center of the screen (0, 0). You can do this as follows: <ul> <li>If the character is below the <tt>y = -100</tt> line, they should not go any lower.</li> <li>If the character is above the <tt>y = 100</tt> line, they should not go any higher.</li> <li>If they are to the left of the <tt>x = -100</tt> line, they should not go any farther left.</li> <li>If they are to the right of the <tt>x = 100</tt> line, they should not go any farther right.</li> </ul> </ul> These blocks may prove helpful: <br /> <div style="text-align: center;"> <img hspace="0" height="65" border="0" width="75" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab03$@SLASH@$Positions.jpg" alt="Positions" title="Positions" /> </div> 1283918478 3982 resource Number-Guessing Game v1.0 html

<h1>Number-Guessing Game v1.0</h1> In the code sample below, we have implemented a simple number-guessing game. The computer chooses a random number and then asks the player to guess the random number. The code is available in <a href="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab03$@SLASH@$GuessTheNumber.sb">this file</a>. <br /><br /> <img hspace="0" height="200" border="0" width="450" vspace="0" title="Number Guesser Starter" alt="Number Guesser Starter" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$GuessANumber_Simple.jpg" /> <br /><br /> The game is not that cool yet, though. In the next few steps, we are going to make the game much more like playing the number-guessing game with a person! 1283924180 3983 resource Number-Guessing Game v2.0 html

<h1>Number-Guessing Game v2.0</h1> We are going to assume that you are comfortable with how the code provided in the previous section works. <br /><br /> Here are six challenges to try to make the code act more like a human! If you think of anything else that would make it cooler, feel free to add it in. Try each of these in order. When you are done, your finished code should be able to deal with <em>all</em> of the challenges. Good luck! <br /><br /> <strong>Challenge #1</strong>: The cat should welcome the player and ask for their name before beginning. <br /><br /> <strong>Challenge #2</strong>: If they guess incorrectly, the cat should tell them that they are incorrect, using their name. For example, if Colleen is playing the game, the cat should say something like <tt>Sorry Colleen, that is not the right answer.</tt> before asking them to guess again. <br /><br /> <strong>Challenge #3</strong>: If they guess incorrectly, the cat should tell them if the secret number is bigger or smaller than the number that they guessed. <br /><br /> <strong>Challenge #4</strong>: Right now, the cat always picks a number between <tt>1</tt> and <tt>10</tt>. Change this so that the cat always picks a number between <tt>1</tt> and a variable named <tt>maximum</tt>. Ask the player what they would like the maximum number to be, before choosing a random number. Use this maximum number as the highest number that the cat will choose. <br /><br /> <strong>Challenge #5</strong>: Keep track of how many guesses it takes before the player guesses the right number. <br /><br /> <strong>Challenge #6</strong>: When the player guesses the secret number, tell them how many guesses it took, and congratulate them using their name. 1283923649 3984 resource Rock, Paper, Scissors: Script html

Let us implement the game! First, make a Scratch script that makes the cat and the duck say either <tt>Rock</tt>, <tt>Paper</tt>, or <tt>Scissors</tt> when the green flag is pressed. <br /><br /> <img hspace="0" height="214" border="0" width="361" vspace="0" title="Rock Paper Scissors Intro" alt="Rock Paper Scissors Intro" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$RockPaperScissorsIntro.jpg" /> <br /><br /> We will implement the rest of the game for homework. 1283921221 3985 resource Homework: Rock, Paper, Scissors html

<h1>Homework: Rock, Paper, Scissors</h1> For this homework, you will make the <em>Rock, Paper, Scissors</em> game more advanced. <h2>Exercises</h2> <ul> <li>Add a third character. After the duck and the cat pick their choice and say it, the third character should say who wins. You may find <a href="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab03$@SLASH@$RPS.pdf">this chart</a> useful.</li> <li>Add <tt>cat score</tt> and <tt>duck score</tt> variables that keep track of how many times each character has won. You can make these variables visible on the stage by clicking on the check-box next to the variable name.</li> </ul> <h2>Upload and Submit</h2> Once you are done, go to the bSpace site and into the <tt>Assignments</tt> tab. Click on <tt>Homework 03</tt> and upload your Scratch solution. Then, press <tt>Submit</tt>. <h2>If You Need a Break</h2> <div style="text-align: center;"> <object width="480" height="385"><param value="http://www.youtube.com/v/NMxzU6hxrNA?fs=1&hl=en_US" name="movie" /><param value="true" name="allowFullScreen" /><param value="always" name="allowscriptaccess" /><embed width="480" height="385" allowfullscreen="true" allowscriptaccess="always" type="application/x-shockwave-flash" src="http://www.youtube.com/v/NMxzU6hxrNA?fs=1&hl=en_US" /> </object> <object width="480" height="385"><param value="http://www.youtube.com/v/iapcKVn7DdY?fs=1&hl=en_US" name="movie" /><param value="true" name="allowFullScreen" /><param value="always" name="allowscriptaccess" /><embed width="480" height="385" allowfullscreen="true" allowscriptaccess="always" type="application/x-shockwave-flash" src="http://www.youtube.com/v/iapcKVn7DdY?fs=1&hl=en_US" /> </object> </div> 1296603027 3986 resource Welcome to BYOB! html

<h1> Welcome to BYOB! </h1> As you have seen, Scratch is a powerful language that has a substantial repository of useful blocks for a variety of purposes. However, as you may have noticed, Scratch does not have all the blocks that you may need, and often, it would prove useful if we could create new blocks. <br /> <br /> Enter BYOB, a language based on Scratch, with the added ability to create new blocks. To get started on BYOB, click on this little guy in your dock: <div style="margin-left: 40px;"> <img vspace="0" hspace="0" border="0" title="'make a block'" alt="'make a block'" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$Square$@SLASH@$Alonzo.jpg" /> </div> <br /> His name is Alonzo, and he is the mascot of BYOB. If you would like to work on BYOB at home, you can download it at <a href="http://byob.berkeley.edu">http://byob.berkeley.edu</a>. <h2> Make Your Own Block: A Tutorial </h2> We are going to teach the computer how to draw a square using a block named <tt>draw square</tt>. Please follow the steps below: <br /> <ol> <li>Click on <tt>make a block</tt> at the bottom of the variables tab (or right-click on the scripting area and choose "<tt>make a block</tt>") <br /> <div style="margin-left: 40px;"> <img width="98" vspace="0" hspace="0" height="44" border="0" title="'make a block'" alt="'make a block'" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$Square$@SLASH@$MakeABlock.jpg" /> </div> </li> <li>This will open up the <tt>make a block</tt> dialog box. Now, you get to choose which tab the block should go into. Our block is going to draw a square, so let us choose <tt>Motion</tt>.<br /> <div style="margin-left: 40px;"> <img width="324" vspace="0" hspace="0" height="380" border="0" title="'make a block' dialog box" alt="'make a block' dialog box" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$Square$@SLASH@$MakeABlockDialog.jpg" /> <br /> </div> </li> <br/> <li>When we selected <tt>Motion</tt>, the block became blue. We now have the option of making blocks of different shapes. Right now, however, we are just going to make a (regular) command block.<br /> <br/> <div style="margin-left: 40px;"> <img width="322" vspace="0" hspace="0" height="370" border="0" title="Make a command block" alt="Make a command block" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$Square$@SLASH@$MakeABlockSquare.jpg" /><br /> </div> </li> <br/> <li>When we click <tt>OK</tt>, we should see the block editor below. (For now, do not worry about the <tt>atomic</tt> check box.) <br /><br/> <div style="margin-left: 40px;"> <img width="436" vspace="0" hspace="0" height="405" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$Square$@SLASH@$EmptyDrawSquare.jpg" alt="Block Editor for 'draw square'" title="Block Editor for 'draw square'" /><br /> </div> </li> <br/> <li>Use the blocks from the regular menus to create a script that draws a square, as shown below. <br /> <br/> <div style="margin-left: 40px;"> <img width="142" vspace="0" hspace="0" height="127" border="0" title="Script to draw a square" alt="Script to draw a square" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$Square$@SLASH@$MakeABlockSquareCode.gif" /> <br /> </div> </li> <br/> <li>When you click <tt>OK</tt>, you should be able to use this block as if it were a regular block. Since you created the block as a <tt>Motion</tt> block, it will end up at the bottom of the <tt>Motion</tt> tab. <br /> <br/> <div style="margin-left: 40px;"> <img width="79" vspace="0" hspace="0" height="48" border="0" title="Using the 'draw square' block" alt="Using the 'draw square' block" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$Square$@SLASH@$RunSquareNoArgs.gif" /><br /> </div> </li> <br/> Congratulations! You have just created your own block! Go on and take a bow. :-) </ol> <h2> Improving the <tt>draw square</tt> block </h2> You have created a block that draws a square, but it only draws a square where each side is of length <tt>100</tt> steps. It would be great if we could specify how long we wanted each side to be. We will edit the block to accept an <em>argument</em> (or <em>input</em>), which tells it the length of the square it has to draw. <ol> <li>We are going to go back and edit the block. Right-click on the new block and select <tt>edit</tt> to go back to the block editor. <br /> <br/> </li> <div style="margin-left: 40px;"> <img width="159" vspace="0" hspace="0" height="119" border="0" title="Editing the 'draw square' block" alt="Editing the 'draw square' block" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$Square$@SLASH@$EditCurrentBlock.jpg" /> <br /> </div> </li> <br/> <li>In the <tt>Block Editor</tt>, notice that when you move the mouse over the top row of the new block, some plus signs (<tt>+</tt>) show up. When you click on these plus signs, you can add more text or arguments. When you click on the text between the plus signs, you can delete or modify that text. Click on the plus sign at the far right as shown below: <br /> </li> <br/> <div style="margin-left: 40px;"> <img width="444" vspace="0" hspace="0" height="412" border="0" title="Plus signs" alt="Plus signs" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$Square$@SLASH@$SquarePlus.jpg" /> <br /> </div> </li> <br/> <li>When you click on the plus sign on the far right, you should get the following dialog box. With this dialog box, we can select if we want to add input (orange) or more text (blue). We want to add the input <tt>size</tt>, so we type <tt>size</tt>, select <tt>Input Name</tt> and click <tt>OK</tt>.<br /> </li> <br/> <div style="margin-left: 40px;"> <img width="316" vspace="0" hspace="0" height="208" border="0" title="Adding an argument to the 'draw square' block" alt="Adding an argument to the 'draw square' block" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$Square$@SLASH@$AddArgument.jpg" /><br /> </div> <li>Now, we have a variable inside our block definition. <br /> <br/> </li> <div style="margin-left: 40px;"> <img width="170" vspace="0" hspace="0" height="133" border="0" title="New variable in the 'draw square' block" alt="New variable in the 'draw square' block" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$Square$@SLASH@$SquareWithSize.gif" /><br /> </div> <br/> <li>Drag the variable <tt>size</tt> down into the move block. Whenever we need a new copy of a variable, we just grab the copy from that variable in the top row.<br /> <br/> </li> <div style="margin-left: 40px;"> <img width="170" vspace="0" hspace="0" height="137" border="0" title="Adding a variable to the body" alt="Adding a variable to the body" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$Square$@SLASH@$SquareWithSizeInBody.jpg" /><br /> </div> <br/> <li>When we click <tt>OK</tt>, we wll see that our <tt>draw square</tt> block now takes an argument. We can put different numbers in the blank and draw squares of different sizes!<br /> </li> <br/> <div style="margin-left: 40px;"> <img width="110" vspace="0" hspace="0" height="48" border="0" title="Running the 'draw square' block with an argument" alt="Running the 'draw square' block with an argument" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$Square$@SLASH@$RunSquareWithArgument.gif" /> </div> </ol> 1296436611 3987 resource Make a "Draw Shape" Block html

<h1>Make a <tt>draw shape</tt> Block</h1> Now, you are going to make a block that takes two inputs. We want to create a <tt>draw shape</tt> block that takes a number of sides and a number of pixels for the length of each side. We will call these input arguments <tt>n</tt> and <tt>pixel</tt>. This exercise should be done with a partner, so introduce yourself to your neighbor and get started on the exercise together! <br /><br /> By the way, you can create the inputs to this block in exactly the same way as we did in the previous section, by clicking on the plus signs to add input; however, as a shortcut, you can also type the names of the input as shown below. <br/> <br /> <div style="margin-left:40px;"><img hspace="0" height="361" border="0" width="300" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$DrawShape$@SLASH@$UsingPercentSigns.jpg" alt="Using percent signs to indicate variables" title="Using percent signs to indicate variables" /></div> <br /> The percent signs (<tt>%</tt>) indicate that the word should be an input. We want you to feel comfortable with both entry methods. <br/> <br/> Unfortunately, the size of the text field where you can type in the name of the block (and any %input shortcuts) is limited. If you find yourself running out of room, we recommend that you just name the block and use the plus signs later to add inputs. 1296424942 3988 resource The Max Block html

<h1> The <tt>Max</tt> block </h1> We will now make a different kind of block -- a <em>reporter</em> block. To demonstrate this, we will make a block called <tt>max</tt> that takes two numbers as input and reports the bigger value (the maximum). <br /> <br /> <img border="0" width="146" vspace="0" hspace="0" height="70" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$Max$@SLASH@$ExecuteMax.jpg" alt="There should be an image here" title="There should be an image here" /> <br /> <br /> <ol> <li>Click <tt>Make a block</tt> and select the <tt>Operators</tt> tab. We want a reporter block. This will give the block its round shape as shown above. As the name implies, reporter blocks can report a value. In the image below, you can see that we used the <tt>%</tt> shortcut for making input variables. <br /> <br /> </li> <img border="0" width="323" vspace="0" hspace="0" height="383" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$Max$@SLASH@$maxMakeABlock.jpg" alt="There should be an image here" title="There should be an image here" /><br /> <li>This should give you a blank <tt>Block editor</tt>. Notice the words <tt>report: something</tt>. You can either type where it says <tt>something</tt>, or you can drag other blocks there. We need to figure out what should be reported.<br /> </li> <br /> <img border="0" width="441" vspace="0" hspace="0" height="409" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$Max$@SLASH@$maxBlockEditor.jpg" alt="Block editor for the 'max' function" title="Block editor for the 'max' function" /><br /> <br /> To keep track of the value to be reported, we are going to make another variable: <br /> <br /> Use a <tt>Script Variables</tt> block. You can click on the name of the variable and change it to <tt>bigger value</tt>.<br /> <br /> <img border="0" width="442" vspace="0" hspace="0" height="409" title="Max, Option 1" alt="Max, Option 1" src="../../../../file.php/13/Images/Lab03/max.jpg" /> <br /><br /> We can use an <tt>if/else</tt> block to set the variable <tt>bigger value</tt> to either <tt>x</tt> or <tt>y</tt>. <br /> Drag a <tt>set</tt> block into the <tt>Block Editor</tt> from the regular variables menu. <br /> You can click on the down arrow on the <tt>set</tt> block to select <tt>bigger value</tt>. <br /> Then, you will drag the <tt>bigger value</tt> variable into the box next to <tt>report</tt>. <br /> Now, click <tt>OK</tt> and try the block out!<br /> </ol> 1296441016 3989 resource Input types html

<h1> Input Types </h1> Unfortunately, we have a bug with our <tt>max</tt> block! We wanted the <tt>max</tt> block to work only for numbers. Yet, you can type text in! <br /> <br /> <div style="margin-left: 40px;"> <img width="191" vspace="0" hspace="0" height="63" border="0" title="Max can also take text" alt="Max can also take text" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$max_input_values$@SLASH@$maxCatDog2.jpg" /><br /> </div> <br /> We are going to limit the <tt>max</tt> block to accept only numbers as arguments. <ol> <li>Open the <tt>Block Editor</tt> for the <tt>max</tt> block and click on the input <tt>x</tt>. <br /> <div style="margin-left: 40px;"> <img width="319" vspace="0" hspace="0" height="206" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$max_input_values$@SLASH@$MaxVariables.jpg" alt="Editing input 'x'" title="Editing input 'x'" /> </div> </li> <br /> <li>Then, click on the right arrow in the pop-up box shown above. This will open the dialog box shown below. This allows us to specify the shape of the slot. We want a numbers-only slot (as shown selected below). We can also specify that we want the variable to have a <em>default</em> value; this is similar to blocks like <tt>move</tt> that always start out with the default value <tt>10</tt>.</li> <br /> <div style="margin-left: 40px;"> <img width="551" vspace="0" hspace="0" height="426" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$max_input_values$@SLASH@$InputType.jpg" alt="Input Type" title="Input Type" /><br /> </div> </li> <br /> <li>Modify both the <tt>x</tt> and <tt>y</tt> variables to take only numbers and to have the default values of <tt>5</tt> and <tt>10</tt>, respectively. Your <tt>Block Editor</tt> should then look like this, with the default values shown in the header. <br /> <br /> <div style="margin-left: 40px;"> <img width="440" vspace="0" hspace="0" height="408" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$max_input_values$@SLASH@$DefaultValues.jpg" alt="Default Values" title="Default Values" /><br /> </div> </li> <br /> <li>When you click <tt>OK</tt>, you should be able to see your block in the <tt>Operators</tt> tab, with the default values filled in. Also, note that you will no longer be able to enter text.<br /> <br /> <div style="margin-left: 40px;"> <img width="124" vspace="0" hspace="0" height="32" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$max_input_values$@SLASH@$max_with_defaults_block.jpg" alt="'max' block with defaults" title="'max' block with defaults" /><br /> </div> </ol> <em>Note</em>: Maybe we <em>did</em> want the <tt>max</tt> block to work with words! However, for the <tt>draw square</tt> and <tt>draw shape</tt> blocks, we definitely only wanted numbers. Modify those blocks to only take in numbers. 1296437002 3990 resource Composition of Functions html

<h1> Composition of Functions </h1> Our custom-made blocks are blocks like any other, and we can use them in other block definitions. To demonstrate this, we are going to make a block that computes the maximum of three values. <br /> <br /> <div style="margin-left: 40px;"> <img width="310" vspace="0" hspace="0" height="372" border="0" title="There should be an image here" alt="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$Max_with_3_Args$@SLASH@$max3Args.jpg" /><br /> </div> <br /> Repeat the steps from the last tutorial to make this version of the <tt>max</tt> block also only take numbers. Then, in the script for the block, we can use two copies of our <tt>max</tt> block. <br /> <br /> <div style="margin-left: 40px;"> <img width="452" vspace="0" hspace="0" height="410" border="0" title="Script for 'max' with three arguments" alt="Script for 'max' with three arguments" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab03$@SLASH@$max3.jpg" /> <br /> </div> <br /> <font size="+1"><em>Note</em>: Make sure you un-check <tt>atomic</tt></font>. <h2> More Practice </h2> Your challenge is to make the following two blocks work: <ol> <li>A three-argument addition operator that only accepts numbers. <div style="margin-left: 40px;"> <br /> <img width="82" vspace="0" hspace="0" height="18" border="0" title="Three-argument addition operator" alt="Three-argument addition operator" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$Max_with_3_Args$@SLASH@$3argPlusExample.gif" /> <br /> </div> </li> <br /> <li>A three-argument <tt>join</tt> operator that has the default values shown below and only accepts text. <div style="margin-left: 40px;"> <br /> <img width="167" vspace="0" hspace="0" height="18" border="0" title="Three-argument join operator" alt="Three-argument join operator" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$Max_with_3_Args$@SLASH@$3argJoin.gif" /> </div> </li> </ol> 1296437076 3991 resource Predicates html

<h1> Predicates </h1> We want to make our own <em>predicate</em>, a kind of block that reports either <tt>true</tt> or <tt>false</tt>. We have a "greater than" operator (<tt>></tt>), an "equal" operator (<tt>=</tt>), and a "less than" operator (<tt><</tt>), but we want a new "greater than or equal to" (<tt>>=</tt>) operator. <ol> <li>We will create the new block and select the <tt>predicate</tt> shape.<br /> <br/> <div style="margin-left: 40px;"> <img width="323" vspace="0" hspace="0" height="370" border="0" title="Greater than or Equal Operator" alt="Greater than or Equal Operator" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$GreaterThanOrEqual$@SLASH@$greaterthanOrEqual.jpg" /><br /> </div> <br/> </li> <li>This gives a <tt>Block Editor</tt> that has a predicate-shaped blank at the bottom. There, we need to place the predicate that we want to report.<br /> <br/> </li> <div style="margin-left: 40px;"> <img width="441" vspace="0" hspace="0" height="405" border="0" title="Greater than or Equal Operator Block Editor" alt="Greater than or Equal Operator Block Editor" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$GreaterThanOrEqual$@SLASH@$GreaterORequal_emptyBlockEditor.jpg" /><br /> </div> <br/> <li>We can fill that in with a composition of a "greater than", "or", and "equal" operators. Make this with your partner and then try it out. Notice that this predicate block reports either <tt>true</tt> or <tt>false</tt>.<br /> </li> <br/> <div style="margin-left: 40px;"> <img width="435" vspace="0" hspace="0" height="412" border="0" title="Greater than or Equal Operator Block Editor" alt="Greater than or Equal Operator Block Editor" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$GreaterThanOrEqual$@SLASH@$GreaterOrequal_Code.jpg" /> </div> </ol> 1296437187 3992 resource Predicates: Make a "Between" block html

<h1>Predicates: Make a <tt>between</tt> block</h1> Create a new predicate block that determines if a number is between two other numbers. The block should return <tt>true</tt> if the first number is between the two numbers or if it is equal to either of the numbers. <br /><br /> <div style="margin-left: 40px;"><img hspace="0" height="18" border="0" width="159" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$Predicates$@SLASH@$between.gif" alt="'between' block" title="'between' block" /> <br /></div> 1284391456 3993 resource Difference between Arguments/Input and Variables html

<h3> Different Kinds of Variables</h3>We've seen a lot of different types of variables. <br /> <ul> <li><span style="font-weight: bold;">Normal/Global variables: </span>These variables are made in the regular menu and can be used ANYWHERE! The variable "score" below is an example. <span style="font-style: italic;">These can be used by any sprite, in any block or in any script.</span><br /></li> </ul> <div style="margin-left: 80px;"><img border="0" width="217" vspace="0" hspace="0" height="332" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab03$@SLASH@$Global_Variable.jpg" alt="Global Variable" title="Global Variable" /><br /></div> <ul> <li><span style="font-weight: bold;">Sprite Specific Variables:</span> When you create a "normal/global" variable you can select that the variable is "For this sprite only". Then these variables will show up as variables listed below the line in the variables tab. <span style="font-style: italic;">We recommend not using these variables in blocks.</span><br /></li> </ul> <div style="margin-left: 80px;"><img border="0" width="300" vspace="0" hspace="0" height="173" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab03$@SLASH@$ForTHisSpriteOnly.jpg" alt="For this sprite only" title="For this sprite only" /> <img border="0" width="214" vspace="0" hspace="0" height="242" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab03$@SLASH@$SpriteVariablesBelowLine.jpg" alt="Below the line" title="Below the line" /><br /></div> <ul> <li><span style="font-weight: bold;">Arguments to a function</span>: A variable set by the person calling the function. We also refer to this as "<span style="font-weight: bold;">input</span>". <span style="font-style: italic;">This can ONLY be used within the block editor. </span><br /></li> </ul> <div style="margin-left: 80px;"><img border="0" width="170" vspace="0" hspace="0" height="137" title="There should be an image here" alt="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$Variables$@SLASH@$Square_with_Size_2.gif" /><br /></div><br /> <ul> <li><span style="font-weight: bold;">Script Variables</span>: The "script variable" block gives us a variable that we can use inside of this script.<span style="font-style: italic;">These can only be used in that particular script. The script could be a block script (shown below) or a regular script.</span><br /></li> </ul> <ul>  </ul> <div style="margin-left: 80px;"><img border="0" width="197" vspace="0" hspace="0" height="193" title="There should be an image here" alt="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$Variables$@SLASH@$max_blockVariable.gif" /></div> 1296439786 3994 resource Conflicts between regular variables and block variables html

We would like to point out something about accessing regular variables when we're in the block editor. In the current situation we have the regular variables, x, y and z (shown below). <br /> <div style="margin-left: 40px;"><img border="0" width="213" vspace="0" hspace="0" height="248" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$Conflicts_between_global_and_block_variables$@SLASH@$variablesXYZ.jpg" alt="There should be an image here" title="There should be an image here" /><br /></div><br />We have made a block that takes arguments named x and y. When we use a "set" block, we click on the drop down menu to see what variables are available to us. Notice that the first variable show is z. This is the regular variable z. Then below the line are the variables x and y. We have made the input names the same as the regular variables x and y so we can no longer access those regular variables!<br /><br /> <div style="margin-left: 40px;"><img border="0" width="387" vspace="0" hspace="0" height="287" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$Conflicts_between_global_and_block_variables$@SLASH@$variables_which_are_available.jpg" alt="There should be an image here" title="There should be an image here" /><br /></div>Now if we add another block variable z in our block editor, we are no longer able to access the regular variable z. (See the image below)<br /><br /><img border="0" width="387" vspace="0" hspace="0" height="287" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$Conflicts_between_global_and_block_variables$@SLASH@$variables_z_global_no_longer_accessible.jpg" alt="There should be an image here" title="There should be an image here" /><br /><br />Here are two ways to think about why this is the way it works: <br /> <ul> <li>The block variables is that they "block" access to regular variables with the same name. <br /> </li> <li>When we use a variable named x inside the block editor, Scratch has to figure out which variable we are referring to. It starts by looking at the block variables. If there is one there, it assumes you mean that variable. If there is no variable in the block that has that name, it assumes you mean the regular variable. <br /> </li> </ul> <br /> 1296440698 3995 resource Simplifying a tic-tac-toe board drawer using functions html

<h1>Simplifying a tic-tac-toe board drawer using functions</h1> In the previous lab, we used a <tt>repeat</tt> block to avoid duplicating code. Similarly, we can use a function to avoid duplicating code. Below is some code to draw a tic-tac-toe board. Your goal is to create functions that make this code simpler. One important thing to keep in mind is to give your new functions really intuitive names, so that it is easy to read the code and understand what it does. <br /><br /> <div style="margin-left: 40px;"> <img width="146" vspace="0" hspace="0" height="642" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$tictactoe$@SLASH@$TicTacToeBoard.gif" alt="Tic-Tac-Toe Board Drawer" title="Tic-Tac-Toe Board Drawer" /></div> 1284391869 3996 resource Homework: Brick Wall html

<h1>Homework: Brick Wall</h1> Sometimes, when we write programs and scripts, it feels like we have hit a brick wall! (This is a good sign - it is supposed to be hard!) For homework, we are going to draw this brick wall. <h2>Exercises and Hints</h2> This homework is not just about drawing; it is also about practicing abstraction. You will draw the following brick wall by implementing the blocks listed below. <div style="margin-left: 40px;"> <img border="0" width="392" vspace="0" hspace="0" height="219" title="Sample image of brick wall" alt="Sample image of brick wall" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$Brick_Wall$@SLASH@$SampleImage.jpg" /> </div> <br /> <em>Note</em>: You must implement these blocks and adhere to the abstraction described below. <br /><br /> There are two kinds of rows in this brick wall: <ul> <li><strong>Row A</strong>: <img border="0" width="334" vspace="0" hspace="0" height="26" title="Row A" alt="Row A" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$Brick_Wall$@SLASH@$Row1.jpg" /></li> <li><strong>Row B</strong>: <img border="0" width="330" vspace="0" hspace="0" height="16" title="Row B" alt="Row B" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$Brick_Wall$@SLASH@$Row2.jpg" /></li> </ul> <br /> The big idea is that there are three levels of abstraction. <br /><br /> <strong>At the lowest level of abstraction (Level 3)</strong>: <br /> <ul> <li>You need to figure out how to draw individual bricks, small bricks and spaces. </li> <li>This level of abstraction contains the following blocks:</li> <ul> <li>The <tt>Draw Brick</tt> block, which draws a single brick.</li> <li>The <tt>Draw Small Brick</tt> block, which draws the small brick for the edges of row B. Note that this brick will <em>not</em> be exactly half as long as the full brick. Part of this homework is figuring out how long the "small brick" should be.</li> <li>The <tt>Draw Space</tt> block, which draws a space between each brick or small brick.</li> </ul> </ul> <br /> <strong>At the middle level of abstraction (Level 2)</strong>: <br /> <ul> <li>You can use the functionality provided by the bottom level of abstraction to make entire rows of bricks.<br /></li> <li>The rows referred to as "Row A" and "Row B" should look like the rows shown above.</li> <li>This level of abstraction contains the following blocks:</li> <ul> <li>The <tt>Initialize Pen</tt> block, which should initialize the pen color and size.</li> <li>The <tt>Initialize Character Position and Direction</tt> block, which should initialize the position and direction of the character.</li> <li>The <tt>Draw Row A</tt> block, which should draw a single copy of Row A.</li> <li>The <tt>Draw Row B</tt> block, which should draw a single copy of Row B.</li> <li>The <tt>Transition between Row A and B with __ space</tt> block, which should transition between the end of Row A and the beginning of Row B, leaving a space as wide as the number of pixels specified by the input argument.</li> <li>The <tt>Transition between Row B and A with __ space</tt> block, which should transition between the end of Row B and the beginning of Row A, leaving a space as wide as the number of pixels specified by the input argument.</li> </ul> </ul> <br /> <strong>At the highest level of abstraction (level 1)</strong> <br /> <ul> <li>You will put together the full brick wall using only the functionality provided by the middle level of abstraction. </li> <li>This level of abstraction contains only the <tt>Draw a Brick Wall with __ rows</tt> block, which draws a brick wall with the specified number of rows.</li> </ul> In summary, you should implement the following blocks: <br /><br /> <div style="margin-left: 40px;"> <img border="0" vspace="0" hspace="0" title="Blocks to implement" alt="Blocks to implement" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$Brick_Wall$@SLASH@$BrickBlocks.gif" /> </div> <br /><br /> <em>Note</em>: Whenever you need to refer to a number in the program, use a variable. This is generally considered good style, because you can use the same variable in multiple places in your program, and you only need to change the value of the variable to change it in multiple places at once. <h2>Upload and Submit</h2> Once you are done, go to the bSpace site and into the <tt>Assignments</tt> tab. Click on <tt>Homework 04</tt> and upload your BYOB solution, as a file called <tt>Brick-Wall</tt>. 1296603506 3997 resource Make a List html

<h1>Make a List</h1> We are going to start working with lists! Lists are a type of <strong>data structure</strong>, a particular way of storing data. Many objects can be easily stored in a list, and so lists have become a very useful and ubiquitous data structure in computer science. For example, if we are developing a game and we want to keep track of the people that have played our game, we might keep their names in a list. <br /><br /> As with anything new, the first thing to do is explore! Make a new list named <tt>players</tt> by clicking on the button <tt>Make a list</tt>, as shown below. <br /><br /> <div style="text-align: center;"> <img hspace="0" height="191" border="0" width="213" vspace="0" title="Make a List" alt="Make a List" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab05$@SLASH@$Lists$@SLASH@$MakeAList.jpg" /> </div> <br /><br /> Below the name of your new list, you will see a bunch of blocks that operate on lists. With your partner, use the <tt>players</tt> list to experiment with these blocks, and determine what these blocks do before going on to the next step. <br /><br /> <div style="text-align: center;"> <img hspace="0" height="404" border="0" width="276" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab05$@SLASH@$Lists$@SLASH@$ListBlocks.jpg" alt="List Blocks" title="List Blocks" /> </div> <br /><br /> <strong>Important note</strong>: In today's lab, and in the labs to come, we will be making a lot of scripts that will be used later. Please be sure to perform each exercise in a different file, and store these files safely in your account. Since you will be programming in pairs, one of you can e-mail the files to the other to ensure that both of you have the files. 1284561645 3998 resource Read a List of Names html

<h1>Read a List of Names</h1> The following script is intended to keep track of the names of the players of a game, but it has a bug! Find and fix the bug. The code is available <a href="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab05$@SLASH@$Lists$@SLASH@$BuggyReadingList.ypr">here, as a BYOB file</a>. Once you are done with it, you may find it useful in your other projects. <br /><br /> <div style="margin-left:40px;"><img hspace="0" border="0" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab05$@SLASH@$Lists$@SLASH@$BuggyReadingList.jpg" alt="Buggy list of names" title="Buggy list of names" /></div> 1284560734 3999 resource Process a List html

<h1>Process a List</h1> We want to have the character read all of the names from our <tt>players</tt> list. This is a very common type of problem when dealing with lists: we want to do the same thing for each item in the list. To tackle this problem, we are going to use a variable called <tt>index</tt> to keep track of the position of the element in the list we are processing. <br /><br /> <div style="margin-left: 40px;"> <img hspace="0" height="156" border="0" width="282" vspace="0" title="Reading the names of the players in the list" alt="Reading the names of the players in the list" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab05$@SLASH@$Loops$@SLASH@$ReadPlayerList.jpg" /></div> <br /><br /> Once you get the script above to work, try to make a script that will read all of the player names and then say them all together, with the appropriate commas, spaces, and the word <tt>and</tt>, as shown below. Remember to save your work! <br /><br /> <div style="margin-left: 40px;"><img hspace="0" border="0" vspace="0" style="width: 434px; height: 233px;" title="Names all together" alt="Names all together" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab05$@SLASH@$Loops$@SLASH@$NamesAllTogether.jpg" /></div> <br /><br /> <em>Hint</em>: Before you make the final result with the commas and <tt>and</tt>, try to make a script that just joins all the names into one variable, and then says that variable. 1284560749 4000 resource Practice with Index Variables html

<h1>Practice with Index Variables</h1> As we have seen in the previous section, we generally use an index variable to process the elements of a list. Below, we have reproduced the script that makes the character say the names of the players in a list. <br /><br /> <div style="margin-left:40px;"><img hspace="0" height="156" border="0" width="282" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab05$@SLASH@$Loops$@SLASH@$ReadPlayerList.jpg" alt="Reading the names of the players in the list" title="Reading the names of the players in the list" /></div> <br /><br /> Modify the script to make the character say the following: <ul> <li>Every other name in a list.</li> <li>Every third name in a list.</li> <li>Names in a list in reverse order.</li> <li>Names in a list that start with the letter <tt>C</tt>.</li> <li>Names that are longer than four letters.</li> </ul> Remember to save your work! 1284959148 4001 resource Remove List Elements html

<h1>Remove List Elements</h1> The script below is supposed to remove all of the occurrences of <tt>ABC</tt> from the <tt>players</tt> list. Find a list for which the script below would not remove all occurrences of <tt>ABC</tt>, and explain your finding. The script is available <a href="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab05$@SLASH@$RemoveABC$@SLASH@$RemoveEntries.ypr">here, as a BYOB file</a>. <br /><br /> <div style="margin-left: 40px;"> <img width="282" vspace="0" hspace="0" height="229" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab05$@SLASH@$RemoveABC$@SLASH@$RemoveEntries.gif" alt="Remove Entries" title="Remove Entries" /> </div> 1284554105 4002 resource Remove List Elements: Take Two html

<h1>Remove List Elements: Take Two</h1> As we have noticed in the previous two sections, a really common bug is to change the state of a list, while you are using the <em>same</em> list to control how many times you are looping. Rewrite the script that removes elements from list using a <tt>repeat until</tt> block. <br /><br /> <div style="margin-left:40px;"> <img hspace="0" border="0" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab05$@SLASH@$RemoveABC$@SLASH@$RepeatUntilBlock.jpg" alt="'repeat until' block" title="'repeat until' block" /> </div> <br /> Remember to save your work! 1284560254 4003 resource Range of List Elements html

<h1>Range of List Elements</h1> Often, we will also want to use a range of values in a list. The first two scripts below allow the character to say the values of a range of list elements. Before testing them, however, think about whether they also include the elements at the start and end indexes. Then, fill in the blank in the third script with a <tt>repeat</tt> block (and not a <tt>repeat until</tt> block), such that it does the same thing as the middle block. <br /><br /> <div style="margin-left: 40px;"> <img hspace="0" height="433" width="282" vspace="0" border="0" title="Getting a range of values" alt="Getting a range of values" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab05$@SLASH@$Loops$@SLASH@$RangeOfValues.gif" /> </div> 1284554029 4004 resource Processing a Sentence html

<h1>Processing a Sentence</h1> The pattern of using an index variable to process a bunch of values is pretty common in programming, and is not specific to lists alone! The block on the left below is the one that we used to say all of the names in our player list. The block on the right can be used to say all of the letters in a sentence like <tt>Go Bears!</tt>. <br /><br /> <div style="margin-left: 40px;"> <img hspace="0" height="156" width="282" vspace="0" border="0" title="Reading the names of the players in the list" alt="Reading the names of the players in the list" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab05$@SLASH@$Loops$@SLASH@$ReadPlayerList.jpg" /> <img hspace="0" height="173" width="307" vspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab05$@SLASH@$Loops$@SLASH@$IndexInSentence.gif" alt="there should be an image here" title="there should be an image here" /> </div> <br /><br /> There are striking similarities between the two scripts, and so we should be able to perform the same tasks on sentences as those we did on lists. Write blocks that make the character say the following: <ul> <li>Every other letter in a sentence.</li> <li>Every third letter.</li> <li>The letters in reverse order.</li> <li>Say a range of letters, using either a <tt>repeat until</tt> or a <tt>repeat</tt> block. </ul> Often, when writing a script, if we have already written a similar script for another purpose or data structure, we can either modify the script for the new functionality, or we can create a more general function that can be used for both purposes. Do as many exercises as you need, until you feel really comfortable with this general pattern of code, because it is very common. 1284554799 4005 resource Swap List Values html

<h1>Swap List Values</h1> We want to make a block that swaps two rows in a list. The block takes two numbers, representing positions of elements in the list, and a list as its inputs, and it swaps the positions of those elements in the list. <br /><br /> <div style="margin-left: 40px;"> <img hspace="0" height="56" width="277" vspace="0" border="0" title="'swap rows' block" alt="'swap rows' block" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab05$@SLASH@$Lists$@SLASH@$SwapRows$@SLASH@$Empty.gif" /> </div> To do so, we need to do something that we have not done before: take a list in as an argument. The third input, <tt>list</tt>, will be a list. Click on the <tt>rowX</tt> and <tt>rowY</tt> variables and limit their input types to be numbers. Then, click on the <tt>list</tt> variable and limit the input type to be a list. The image below shows the dialog box to select a list from the input type options. <br /><br /> <div style="margin-left: 40px;"> <img hspace="0" height="424" width="548" vspace="0" border="0" title="Dialog box to make an input a list" alt="Dialog box to make an input a list" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab05$@SLASH@$Lists$@SLASH@$SwapRows$@SLASH@$MakeArgList.jpg" /> </div> When you click <tt>OK</tt>, you should be able to see the block with two round number input spots and one list input spot. <br /><br /> <div style="margin-left: 40px;"> <img hspace="0" height="28" width="159" vspace="0" border="0" title="'swap rows' block with list input" alt="'swap rows' block with list input" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab05$@SLASH@$Lists$@SLASH@$SwapRows$@SLASH@$ListInput.gif" /> </div> Inside the <tt>Block Editor</tt>, we can use the <tt>list</tt> variable as a real list, as shown below, where we set the block variable <tt>temp-value</tt> to be the item at <tt>rowX</tt> of <tt>list</tt>. <br /><br /> <div style="margin-left: 40px;"> <img hspace="0" vspace="0" border="0" title="Partial script" alt="Partial script" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab05$@SLASH@$Lists$@SLASH@$SwapRows$@SLASH@$PartialScript.gif" /> </div> Now, complete the definition of the block using the hint given above. Here is an example of how the block will be used: If we run the block with the arguments <br /><br /> <div style="margin-left: 40px;"> <img hspace="0" height="30" width="226" vspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab05$@SLASH@$GameBoard$@SLASH@$SwapRowsExample.gif" alt="Swap Rows" title="Swap Rows" /> </div> where <tt>game board</tt> is the list <div style="margin-left: 40px;"> <img hspace="0" height="229" width="133" vspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab05$@SLASH@$GameBoard$@SLASH@$ListBeforeSwap.gif" alt="Before" title="Before" /> </div> then, the list should become <div style="margin-left: 40px;"> <img hspace="0" height="228" width="127" vspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab05$@SLASH@$GameBoard$@SLASH@$ListAfterSwap.gif" alt="After" title="After" /> </div> 1284557370 4006 resource Check if a List is Sorted html

<h1>Check if a List is Sorted</h1> Now that you are familiar using lists as an argument, work with your partner to make the following predicate block that detects if the elements of a list are in order. <br /><br /> <div style="margin-left: 40px;"> <img width="122" vspace="0" hspace="0" height="20" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab05$@SLASH@$Lists$@SLASH@$IsSorted$@SLASH@$Block.gif" alt="'is list in order?' predicate" title="'is list in order?' predicate" /> </div> <h2>Test Cases</h2> Below, we show an example where your new block should return <tt>true</tt> and where your new block should return <tt>false</tt>. <br /><br /> <div style="margin-left: 40px;"> <img width="317" vspace="0" hspace="0" height="88" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab05$@SLASH@$Lists$@SLASH@$IsSorted$@SLASH@$True.jpg" alt="True case" title="True case" /> <img width="316" vspace="0" hspace="0" height="88" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab05$@SLASH@$Lists$@SLASH@$IsSorted$@SLASH@$False.jpg" alt="False case" title="False case" /> </div> <br /> <em>Note</em>: When comparing two letters, Scratch and BYOB do not care about capital letters: <tt>A</tt> is equivalent to <tt>a</tt>. <br /><br /> You should think about what other good test cases would be. For example, you should think about what should happen if there are no elements or if there is only one element. These test cases check the <strong>corner cases</strong>. The normal test cases, which most people will remember to make, check whether the block works for a list with a lot of elements. However, it is as important to think about what it will do for no elements or one element. This makes your script more <strong>robust</strong>: it allows your script to act properly in case of unexpected or tricky input. <br /><br /> <strong>Stuck?</strong> If you get stuck, we have provided a hint in the next section. <h2>Boolean values</h2> When returning <tt>true</tt> or <tt>false</tt>, make sure that you use the blocks that Scratch and BYOB have provided especially for this purpose, in the <tt>Operators</tt> tab: <br /><br /> <div style="margin-left: 40px;"> <img vspace="0" hspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab05$@SLASH@$Lists$@SLASH@$IsSorted$@SLASH@$BooleanValues.jpg" alt="Boolean values" title="Boolean values" /> </div> <br /> <tt>true</tt> and <tt>false</tt> are known as <strong>boolean values</strong>. Notice that they have a hexagonal shape, which means they can fit into any hexagonal slots. This also means that any block with a hexagonal shape returns boolean values, and in many programming languages -- Scratch and BYOB included -- boolean values are treated as a special <strong>boolean type</strong>. Boolean values are named after George Boole, a 19th century mathematician who first proposed using <tt>true</tt> and <tt>false</tt> as the basis for logical thinking. 1284562169 4007 resource Check if a List is Sorted: Hint html

<h1>Check if a List is Sorted: Hint</h1> You should be reading this if you either got stuck on the exercise in the last section, or if you have finished the exercise. Either way, we still think it would be good to read. <br /><br /> Here are some things to think about: <ul> <li>We want this to return either <tt>true</tt> or <tt>false</tt>. Such blocks are <strong>predicate</strong> blocks, so we need to select the predicate reporter block shape when we make the block.</li> <li>A list is in order if every sequential pair is in the correct order.</li> <li>We can assume that the list is in order until we find evidence that it is not.</li> <li>We are going to need an index variable to step through each pair of elements in the array.</li> <li>It is helpful to create variables (and give names to particular useful information) to keep track of things. For example, in the image below, we chose to make variables <tt>current</tt> and <tt>next</tt> to keep track of the current list element and the next list element, respectively, when we are in the loop that moves through the list. <br /><br /> <div style="margin-left:40px;"> <img width="568" vspace="0" hspace="0" height="245" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab05$@SLASH@$Lists$@SLASH@$IsSorted$@SLASH@$Hint.jpg" alt="Hint" title="Hint" /> </div> </li> </ul> 1284562602 4008 resource Everyone's Got Algorithms html

<h1>Everyone's Got Algorithms</h1> The word "algorithm" is arguably one of the nerdiest words ever emitted from a human mouth. Fortunately for us, the meaning is far easier to understand than you would first think -- an algorithm is simply a set of steps that allow us to solve a particular problem. In fact, many other careers use algorithms, but have different names for them.<br /> <ul> <li><strong>Cooks</strong> use or memorize <em>recipes</em> to prepare food.</li> <li><strong>UPS Truck Drivers</strong> have “340 Methods,” the UPS handbook for drivers, that describes 340 different <em>protocols </em>that should be followed and how long each one should take.</li> <li><strong>Electricians</strong> follow the same general <em>steps</em>when replacing or adding cabling at different houses.</li> <li><strong>Salesman</strong> often have <em>scripts</em> to follow when making a sales call. The scripts describe how to open the conversation (and possibly more) in order to increase the odds of gaining a client.</li> <li><strong>Subway Sandwich Artists</strong> have a <em>series of signs</em> stuck to the inside of the counter that prompt the employees with what should be said.</li> <li><strong>Do-It-Yourself projects</strong> all come with some sort of <em>instructions</em>. <em>Directions</em>, such as those for assembling a piece of furniture or a Lego kit, are algorithms.</li> </ul> Computer science <em>algorithms</em> are conceptual solutions to a problem (such as sorting a list), whereas the <em>implementation</em> of an algorithm is the actual code that brings the solution to life. The implementations themselves can typically be written in almost any programming language and run on any computer; the concepts behind the algorithm are not affected by these types of conditions, in the same way that the outcome of a well-written recipe should (hopefully) not be affected by the cook or kitchen. 1284998446 4009 resource Teacher Resource: Searching & The Need for Speed html

<h2>Searching</h2>Give each group a set of cups (at least 20 recommended, more will prove the point more effectively but take more time) with a number between 1 and 100 written on the bottom of each one. Keep one set of sorted cups for yourself. Distribute the students' cups in a random, non-sequential order so that the students have no idea which cup is which. Designate one member of the group as the "leader," who will be responsible finding a particular cup with the help of his or her teammates.<br /><br />This will simulate a standard data structure (array, linked list, etc) that doesn't use any sort of ordering to store its elements. The fastest way to search for a specific item is to scan the data structure iteratively, which is an O(n) operation.<br /> <h2>The Need for Speed</h2>Ask the students to brainstorm with their group to come up with a way of saving time of this type of operation. Allow them to use their set of cups to experiment and demonstrate any ideas that they have. Hopefully they will think of sorting the cups; if they haven't come up with this after a reasonable amount of time, feel free to nudge them in that direction or explain using your set of cups. If a group does develop this idea, have them demonstrate and explain it to the rest of the class after the other groups have had time to experiment.<br /> 1282536282 4010 resource Activity - Searching html

<h2>Activity - Searching</h2>We're going to step away from the computer for this activity. First things first: divide up into groups. Let’s examine a common computer science problem: finding a number in a list of numbers. We can assume that the user will provide a specific number to look for, and we need to develop an algorithm that will find what location the number they're searching for is located in (or if it's absent). A computer can only check one position in a list at a time, and checking positions takes time. Let's say we're searching through a list where the numbers are random (within a range) and unique (the same number won't be in there twice). As you might imagine, there are several different ways that you can find a particular number in this type of list, but we know that many algorithms have advantages over others. We'll use a set of numbered cups in this activity to represent different pieces of data. Let’s call the number of cups N. <br /><br /><span style="font-weight: bold; font-style: italic;"></span>Our first goal is to find a specific number among a bunch of randomly chosen cups. Using your set of cups as a testbed, work with your group to <span style="font-style: italic;"><span style="font-weight: bold;">develop an algorithm <span style="font-style: italic;"><span style="font-weight: bold;">(remember: set of steps) to do this.</span></span></span></span> Your algorithm should work for any set of random numbers. <span style="font-style: italic;"><span style="font-weight: bold;">D<span style="font-style: italic;"><span style="font-weight: bold;">iscuss the following ideas with your group to help your thought process</span></span></span></span>:<br /> <ul> <li>What strategies exist for finding a particular number in the fewest number of location checks?</li> <li>How many guesses would it take on average to find a number? <br /> </li> <li>How many guesses would it take to determine that a number didn’t exist in the list at all?</li> <li>How much additional work will it be to find a number if N were to increase? <br /></li> </ul> 1282535972 4011 resource Activity - The Need for Speed html

<h2>The Need for Speed</h2>The approach your team developed in the last section is great for situations where you only need to perform a few searches, but is actually too slow for many other uses -- as the number of cups increases, the time it takes to find a single number increases pretty significantly. Let's reconsider the problem: if we have this series of cups, what can we do that will make it easier to find a particular number when a user requests it? Brainstorm on some ideas with your group and come up with a plan that could help us do more searching in less time. One person should prepare to present your group's revised idea to the class. 1284998522 4012 resource The Need for Speed: Teacher Resource html

[For teachers: have students explain why a particular solution would save some time. Demonstrate using the group's cups. If no one suggests sorting the cups, suggest it and ask why that would make the search faster.] 1284998010 4013 resource Algorithms in BYOB html

<h2>Algorithms in BYOB</h2>Using <a href="$@FILEPHP@$$@SLASH@$starting_points$@SLASH@$algorithms-framework.ypr">the framework provided</a>, implement a BYOB block in the <span style="font-weight: bold;">Unsorted</span> sprite that finds a number in a list of unsorted numbers using the strategy that we discussed. The block should accept the target number (the "needle") and a full list of numbers (the "haystack") as arguments, and return the index of the number’s position in the list. What was the strategy we discussed for unsorted lists, and how could you implement it in BYOB? Fill in a separate block for the sorted approach and implement it as well. Use the framework to determine how their running time changes as the list size increases. Which is faster for a list of size 5? 50? 500? 5000? Why do you think this is?<br /><br /> <div style="text-align: center;"><img border="0" width="244" vspace="0" hspace="0" height="89" title="Blocks to build" alt="Blocks to build" src="$@FILEPHP@$$@SLASH@$finder-blocks.png" /><br /></div><br /> <h3>Searching Unsorted Data</h3>Unsorted data doesn't give you a lot to work with. Your knowledge is limited to strictly the most obvious information: the numbers themselves. This makes strategy somewhat non-existent; the best you can do, on average, is to simply start at the beginning and search through the list one by one. This approach can become incredibly slow if we're dealing with a lot of data, but is actually fairly quick when working with smaller amounts of data. In addition, the block is relatively straightforward to create and doesn't require the data to be put into a particular order to work. The block should return the location of the number in the list, or zero if the number doesn't exist in the list.<br /> <h3>Searching Sorted Data</h3><img border="0" width="558" vspace="0" hspace="0" height="452" style="float: right; display: inline;" src="$@FILEPHP@$$@SLASH@$binary-search.png" alt="Searching for Numbers" title="Searching for Numbers" /><br />You could say that putting information in a particular order (lowest => highest, for example) actually <span style="font-style: italic;">creates new</span> information. Instead of being a simple list of numbers, sorting the information adds order and allows us to make additional assumptions that we weren't able to make before. This type of information is different from the numbers themselves: it is not stored in a variable or list, but becomes a <span style="font-style: italic;">property </span>of the information itself. We can use the property to reduce the number of checks we have to do to find a particular number. The trade-off to this, however, is that we need to sort the list (which takes time) before we can make use of the order.<br /><br />The provided framework includes <img border="0" width="64" vspace="0" hspace="0" height="37" title="Sort" alt="Sort" src="$@FILEPHP@$$@SLASH@$sort.png" />, which will allow you to sort a list. Sorting the list will take a decently long time, so we'll want to do it as few times as possible. How many times will you need to sort the list for each test run? <br /><br />Searching through sorted data, while faster, also requires a more complicated block. We won't need to search through every space in the list anymore -- we can assume that many of them won't work. We can keep track of the range of numbers in a list that are a possible solution to the problem (see diagram) by recording the minimum and maximum slots that could possibly contain our number. This range should shrink after each guess because you can throw away the half of the numbers on the wrong side of the center point. Here's how things should generally work:<br /> <ol> <li>The range of possibilities starts off including every number in the list (the minimum is position #1 and the maximum is the final position). Let's say that we're searching for the number 33 as shown in the diagram. Start your search around the middle of the list. Check the value of the number there.</li> <li>If the number at the spot you searched is greater than 33, set the maximum to the slot before the one you just searched (after all, 33 CAN'T be on the larger side if it's is smaller than the one you just checked!). If the number is smaller than 33, set the minimum to the slot after the one you searched.</li> <li>Check the middle position of your new range. Repeat step 2 for this new range and reduce the range further.</li> <li>Continue to repeat steps 2 & 3 until either (a) you find the number you're looking for or (b) you get in a position where the minimum and maximum of the range are equivalent without finding the number. If (b) happens, it means that the number doesn't exist in the list.<br /> </li> </ol> <br /> <h3>Flying Even Higher</h3>Let’s say this application is going to be used to find many numbers every time it is launched -- possibly the same number multiple times. How could we speed this process up even more?<br /> 1297067936 4014 resource Improving Our Number Finder html

<span style="font-weight: bold;">Feel free to ask your GSI for help on this section if you get stuck. We'll be discussing a somewhat difficult subject and it may be helpful to have it explained in person.</span><br /><br />If the user may be searching for the same number multiple times, it seems ridiculous to calculate the answer each time that they ask. Why don’t we remember the answer after it’s been calculated instead? Remembering previously calculated information is called <span style="font-weight: bold;">memoization </span>(not memorization) in computer science. It is a powerful technique that can be used to speed up programs that have redundant calculations.<br /><br />Let’s add a third block to our BYOB project (almost a copy of block #2, the sorted number finder) that uses memoization to remember the location of numbers that have already been found. <br /><br /> <div style="text-align: center;"><img border="0" width="313" vspace="0" hspace="0" height="31" title="Memoized" alt="Memoized" src="$@FILEPHP@$$@SLASH@$memoized.png" /><br /></div>We’ll use a list to keep track of the locations of numbers that we’ve found already: the index of each element in the list will be the number we’re looking for and the corresponding value will be the location where that number was found. If the value at a particular index is -1, that means that we haven’t looked for the number yet and if the value is 0 then that means that the number doesn't exist in the list. Here is an algorithm describing how the new BYOB block should progress using the new memoization list:<br /> <ol> <li>Start off setting all of the slots in <span style="font-style: italic;">memory </span>to -1 because we haven't found any numbers yet.<br /></li> <li>Check the global list <span style="font-style: italic;">memory</span> to determine if the number in question has already been found.</li> <li>If so, report the saved location. If not, we’ll have to calculate it.</li> <li>Find the number’s location using the sorted technique we’ve used in the past.</li> <li>Save the location of the number in the <span style="font-style: italic;">memory </span>list so that we don’t have to go through this pain again.</li> </ol>Each value will now be computed a maximum of one time. Now that’s fast! 1297068069 4015 resource Too Many Blocks! html

<h1>Too Many Blocks!</h1> There’s only one problem with our search project: we’ve got three different blocks that all do the same thing (finding a number in a list). That’s way more complicated than it needs to be...how could we use abstraction to make this clearer and simpler for others who want to find numbers in a list?<br /><br />Here’s a thought: what if we created a single block, “find number x in list y,” that made no mention of how it found the number. The user of the block could assume that it would do what it said without worrying about the technicalities of how it gets it done. Then, even if you started with a terribly slow version of the block, you could easily update the algorithm it used without changing anything outside of the block itself. The input and output would remain the same -- only the steps to get from one to the other would change. This is the beauty of abstraction with algorithms: users are able to assume that a particular block works without having to understand all of the details of the algorithm itself! Did you investigate the sort block included with this lab? You didn’t have to -- you could just assume that it worked!<br /><br />In fact, each of the blocks in BYOB has an algorithm that tells it how to do what it does. Think how much harder it would be to work with BYOB if you had to understand how each block worked before you could use it!<br /> 1285274886 4016 resource Make a Game Board html

<h1>Make a Game Board</h1> In today's lab, we are going to get more practice working with lists by making a representation of a game board. Make a new block as shown below that takes in a list and an <tt>x</tt> and <tt>y</tt> value. It should make a new board with a <tt>B</tt> for every spot (representing a blank). <br /><br /> <div style="margin-left: 40px;"> <img hspace="0" vspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab08$@SLASH@$gameboard_representation$@SLASH@$make_board.gif" alt="There should be an image here" title="There should be an image here" /></div> For example, the board below was made with <tt>x</tt> set to <tt>4</tt> (the number of columns) and <tt>y</tt> set to <tt>6</tt> (the number of rows). <br /><br /> <div style="margin-left: 40px;"> <img hspace="0" height="348" width="219" vspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab08$@SLASH@$gameboard_representation$@SLASH@$GameBoardBlank.jpg" alt="There should be an image here" title="There should be an image here" /></div> <em>Note</em>: We chose to have the block modify the existing list <tt>game board</tt>, instead of reporting a <em>new</em> list, as shown in the example in the image below. Think about how you could make a reporter block like the one below. Remember that there is no <tt>set</tt> block for lists! <br /><br /> <div style="margin-left: 40px;"> <img hspace="0" height="209" width="303" vspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab06$@SLASH@$game_board$@SLASH@$makeABoardReporter.jpg" alt="Game Board" title="Game Board" /></div> 1285176994 4017 resource Get One Piece html

<h1>Get One Piece</h1> Now that we have a game board, we want to be able to get and set the pieces in the game board. Make the block below that takes an <tt>x</tt> value and a <tt>y</tt> value and a list. It should report the character at that spot in the board. For example, if we run the block with <tt>x</tt> = <tt>4</tt> and <tt>y</tt> = <tt>3</tt>, it should report the piece at the third row, fourth column (highlighted in black below). <br /><br /> <div style="margin-left: 40px;"> <img hspace="0" height="22" border="0" width="232" vspace="0" title="Get Piece Block" alt="Get Piece Block" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab08$@SLASH@$gameboard_representation$@SLASH@$get_piece.gif" /></div> <br /> <div style="margin-left: 40px;"><img hspace="0" height="348" border="0" width="219" vspace="0" title="Game Board with Highlighted Piece" alt="Game Board with Highlighted Piece" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab08$@SLASH@$gameboard_representation$@SLASH@$GameBoardHIghlightedSquare.jpg" /> <br /><br /></div> <strong>Hints</strong>: <br /> <ul> <li>You might want to (manually) change the piece that you want to extract to be a different letter (for example, <tt>x</tt>) so that you can see if you successfully got the correct element.</li> <li>The following block will be helpful. Play with it to understand how it works before you use it in the function above.</li> </ul> <div style="margin-left: 40px;"> <img hspace="0" height="18" border="0" width="118" vspace="0" title="there should be an image here" alt="there should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab05$@SLASH@$letterOfWord.gif" /></div> 1285177419 4018 resource Error Checking html

<h1>Error Checking</h1> In the previous step we wrote a block to get a piece from our game board. <br /><br /> <div style="margin-left: 80px;"><img hspace="0" height="22" width="232" vspace="0" border="0" title="There should be an image here" alt="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab08$@SLASH@$gameboard_representation$@SLASH@$get_piece.gif" /><br /></div><br />But what should our block do if we tried to get the 9th row and 100th column in a 4x4 game board? We need to do some error checking to make sure that the arguments passed in are valid. <br /><br />Add error checking code to the get block. If someone calls the block with a column or row outside of the range of the list, the block should report a blank. Make a comment in your "get" block to explain this behavior. <br /><br />For the rest of this lab - make sure that you have error checking code in your blocks! <br /> <div style="margin-left: 80px;"><br /></div> 1285177466 4019 resource Change a Piece Value html

Next we want to change a piece value. <br /><br /> <div style="margin-left: 40px;"><img hspace="0" height="30" width="240" vspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab05$@SLASH@$GameBoard$@SLASH@$SetToA.gif" alt="Set to A" title="Set to A" /><br /></div><br />We will only be working with a single entry in the list, the row <span style="font-family: courier new,courier,monospace;">y</span>. We will be able to use the block below to replace that entry in the list.<br /><br /> <div style="margin-left: 40px;"><br /><img hspace="0" height="26" width="222" vspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab05$@SLASH@$replaceItem.gif" alt="there should be an image here" title="there should be an image here" /></div><br />This is going to be complicated because we need to do four things for that entry:<br /> <ul> <li>Copy the letters (if any) that are less than our input <span style="font-family: courier new,courier,monospace;">x</span> into a new variable</li> <li>Copy the new value onto the end of that variable</li> <li>Copy the letters (if any) that are greater than our input <span style="font-family: courier new,courier,monospace;">x</span> to the end of that variable</li> <li>Replace that row with the new variable</li> </ul>Before you make the block below "Set" that takes in an x and y value, a list and a new character, try to write the block "copy letters" that you can use in the set function. Copy letters should report the letters from a minimum index to a maximum index and should include the letters at both the minimum and maximum index.<br /><br /> <div style="margin-left: 40px;"><img hspace="0" height="69" width="312" vspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab08$@SLASH@$gameboard_representation$@SLASH@$copyLettersWorking.jpg" alt="There should be an image here" title="There should be an image here" /><br /></div><br />The next page has a hint about copy letters. Try to get started before you look at it. 1285177572 4020 resource Copy Letters: Hint html

Here is a hint for copy letters, we gave you a bit of a start and you and your partner should try to fill out the rest. <br /><br />You'll need:<br /> <ul> <li>a variable "index" to keep track of where you are in "word".</li> <ul> <li>This will start at "min".<br /></li> </ul> <li>a variable "copy of letters" to hold the letters you've gathered so far.</li> <ul> <li>This will start out blank<br /></li> </ul> <li>a loop that copies the letters at "index" into "copy of letters"<br /></li> </ul> <div style="margin-left: 40px;"><img border="0" vspace="0" hspace="0" title="There should be an image " alt="There should be an image " src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab08$@SLASH@$gameboard_representation$@SLASH@$CopyLetters.jpg" /></div> 1297281023 4021 resource Change a Piece Value: Take Two html

Now that you have "copy letters" working, we can move on to make set work. Look back at the <a href="$@RESOURCEVIEWBYID*8839@$">previous step</a> about "set" if you need a hint. <br /><br /> <div style="margin-left: 40px;"><img hspace="0" height="30" width="240" vspace="0" border="0" title="There should be an image here" alt="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab08$@SLASH@$gameboard_representation$@SLASH@$set_piece.gif" /><br /></div><br /> <div style="margin-left: 40px;"><img hspace="0" height="69" width="312" vspace="0" border="0" title="There should be an image here" alt="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab08$@SLASH@$gameboard_representation$@SLASH@$copyLettersWorking.jpg" /><br /></div> 1285177624 4022 resource Sorting a List: Helper Functions html

<h1>Sorting a List: Helper Blocks</h1> Now, we will tackle the problem of <em>sorting</em> a list: we have a list of numbers or letters, and we want to arrange them in a particular order. Well, that sounds very complicated, but we can make good use of our function that checks if a list is in order. A common technique when writing programs is to think: <br /><br /> <div style="margin-left: 40px;">"wow this would be simple if I just had a function that did _____"<br /></div><br />We have such a case here! Below we've written a sort function that uses swapping. If we just had a function (that we're calling "swap out of order elements in list") that went through the list once and uses the swap block to swap every out of order element, we could just keep doing that until the list was completely sorted. <br /> <div style="margin-left: 40px;"><img hspace="0" height="123" width="238" vspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab07$@SLASH@$Sort$@SLASH@$SortMethod.gif" alt="Block to sort a list." title="Block to sort a list." /> <br /><br /> </div> What we did is make a "stub" (an unimplemented block that just has the right name and arguments) for this new block and then we used it in our sort function. If we convince ourselves that this would work, we can go on to think about how to write the swap function. <br /><br />To try to break problems down, always look for times when you could say: <br /><br /> <div style="margin-left: 40px;">"wow this would be simple if I just had a function that did _____"<br /> </div> <br /> <ol> <li>Pretend you have that function (even if you're not sure yet how to write it) and make a "stub" of that function.</li> <li>Write your higher level function using the stub. (You won't be able to test this until you actually figure out how to write the stub.)</li> <li>Go to the stub and try to figure out how to write it (hopefully you have another insight of 2 or 3 other functions that if you had them, it would be simple to write the original stub.</li> </ol>Now work with your partner to write the "swap out of order elements in list" function and test it before returning and testing it with your swap function. <br /> 1285167148 4023 resource Sorting a List html

<h1>Sorting a List</h1> In the rest of today's lab, we will tackle the problem of sorting a list: we have a list of numbers or letters, and we want to arrange them in a particular order. We are going to look at one algorithm (out of many!) to sort a list of numbers or words. Whenever we read a new algorithm, we need to step back and see the Big Picture: what task is this algorithm trying to accomplish, and how is it going to approach this task? For this new sorting algorithm, the Big Picture is: <ul> <li>We are going to keep some part of the list always sorted. In other words, we will separate the list into two parts: a <em>sorted</em> part and an <em>unsorted</em> part.</li> <li>Each time a loop runs, we will move one more item up into the sorted section.</li> <li>Eventually, we will have seen every element in the list and we will have placed it into its proper position.</li> </ul> Let us attempt a step-by-step description of this algorithm: <ul> <li>We start off with just the first element, and we already know that the first element, by itself, is already sorted.</li> <li>Next, we add the second element of the list into its correct position, so that the first and second elements are sorted.</li> <li>Next, we add the third element of the list into the correct position so that the first through third elements are sorted.</li> <li>Next, we add the fourth element of the list into the correct position so that the first through fourth elements are sorted.</li> <li>...</li> <li>Finally, we add the last element of the list into the correct position so that the first through last elements are sorted, and the list is itself sorted.</li> </ul> Below, we show the algorithm running on a particular list. Make sure that you understand this algorithm before you proceed. In the next step, you will be writing this program. <br /><br /> <table width="100%" border="1"> <tbody> <tr> <td width="20%" valign="top">Row 1 is sorted.<br /> <img vspace="0" hspace="0" border="0" title="Row 1 is sorted." alt="Row 1 is sorted." src=$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab07$@SLASH@$Sort$@SLASH@$InsertionSort$@SLASH@$Sort01.gif" /><br />(<tt>239</tt> did not need to move.) </td> <td width="20%" valign="top">Rows 1 and 2 are sorted.<br /> <img vspace="0" hspace="0" border="0" title="Rows 1 and 2 are sorted." alt="Rows 1 and 2 are sorted." src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab07$@SLASH@$Sort$@SLASH@$InsertionSort$@SLASH@$Sort02.gif" /><br />(<tt>48</tt> moved up 1 spot into its correct position.)<br /><br /> </td> <td width="20%" valign="top">Rows 1 through 3 are sorted.<br /> <img vspace="0" hspace="0" border="0" title="Rows 1 through 3 are sorted." alt="Rows 1 through 3 are sorted." src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab07$@SLASH@$Sort$@SLASH@$InsertionSort$@SLASH@$Sort02.gif" /><br />(<tt>675</tt> did not need to move.)<br /> </td> <td width="20%" valign="top">Rows 1 through 4 are sorted.<br /> <img vspace="0" hspace="0" border="0" title="Rows 1 through 4 are sorted." alt="Rows 1 through 4 are sorted." src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab07$@SLASH@$Sort$@SLASH@$InsertionSort$@SLASH@$Sort02.gif" /><br />(<tt>790</tt> did not need to move.)<br /> </td> <td width="20%" valign="top">Rows 1 through 5 are sorted.<br /> <img vspace="0" hspace="0" border="0" title="Rows 1 through 5 are sorted." alt="Rows 1 through 5 are sorted." src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab07$@SLASH@$Sort$@SLASH@$InsertionSort$@SLASH@$Sort03.gif" /><br />(<tt>261</tt> moved up 2 spots into its correct position.)<br /> </td> </tr> <tr> <td width="20%" valign="top">Rows 1 through 6 are sorted.<br /> <img vspace="0" hspace="0" border="0" title="Rows 1 through 6 are sorted." alt="Rows 1 through 6 are sorted." src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab07$@SLASH@$Sort$@SLASH@$InsertionSort$@SLASH@$Sort04.gif" /><br />(<tt>430</tt> moved up 2 spots into its correct position.)<br /> </td> <td width="20%" valign="top">Rows 1 through 7 are sorted.<br /> <img vspace="0" hspace="0" border="0" title="Rows 1 through 7 are sorted." alt="Rows 1 through 7 are sorted." src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab07$@SLASH@$Sort$@SLASH@$InsertionSort$@SLASH@$Sort04.gif" /><br />(<tt>210</tt> moved up 5 spots into its correct position.<br /> </td> <td width="20%" valign="top">Rows 1 through 8 are sorted.<br /> <img vspace="0" hspace="0" border="0" title="Rows 1 through 8 are sorted." alt="Rows 1 through 8 are sorted." src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab07$@SLASH@$Sort$@SLASH@$InsertionSort$@SLASH@$Sort06.gif" /><br />(<tt>204</tt> moved up 6 spots into its correct position.)<br /> </td> <td width="20%" valign="top">Rows 1 through 9 are sorted.<br /> <img vspace="0" hspace="0" border="0" title="Rows 1 through 9 are sorted." alt="Rows 1 through 9 are sorted." src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab07$@SLASH@$Sort$@SLASH@$InsertionSort$@SLASH@$Sort07.gif" /><br />(<tt>762</tt> moved up 1 spot into its correct position.)<br /> </td> <td width="20%" valign="top">Rows 1 through 10 are sorted.<br /> <img vspace="0" hspace="0" border="0" title="Rows 1 through 10 are sorted." alt="Rows 1 through 10 are sorted." src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab07$@SLASH@$Sort$@SLASH@$InsertionSort$@SLASH@$Sort08.gif" /><br />(<tt>6</tt> moved up 9 spots into its correct position.)<br /> </td> </tr></tbody> </table> 1285173697 4024 resource Sorting a List: Implementation html

<h1>Sorting a List: Implementation</h1> We can describe the general algorithm from the last step using the following block of code: <br /><br /> <div style="margin-left: 40px;"> <img hspace="0" border="0" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab05$@SLASH@$insertion_sort_code.gif" alt="Insertion sort code" title="Insertion sort code" /></div> <br /> We have not written the <tt>move-up into position</tt> block yet; it is just a <em>stub</em>, a block without a script. <br /><br /> The <tt>move-up into position</tt> block should take a number at a particular index (<tt>index</tt>) and swap it with the number just above it. The block should repeat this step until that number is either at the top of the list, or it is below a smaller number. This way, the number at <tt>index</tt> is placed into its correct position in the sorted portion of the list (check it!). In an earlier lab, you implemented a block that <a href="$@RESOURCEVIEWBYID*8821@$">swaps two rows in a list</a>; you may find this block useful. <br /><br /> Complete the <tt>move-up into position</tt> block so that the <tt>swap-insertion sort</tt> block works. You can download the framework code <a href="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab05$@SLASH@$insertion-sort.ypr">here</a>. 1285178288 4025 resource Optional: Sorting a Word html

<h1>Optional: Sorting a Word</h1> You are now going to write the swap-insertion sort again, except this time for words instead of lists! (This is an optional section, meant for extra practice.) <br /><br /> <div style="margin-left: 40px;"> <img hspace="0" height="308" width="294" vspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab05$@SLASH@$SwapExamples.jpg" alt="Swap examples" title="Swap examples" /> </div> <br /> We already have some parallels between functions for words and functions for lists: <br /><br /> <div style="margin-left: 40px;"> <img hspace="0" height="58" width="288" vspace="0" border="0" title="There should be an image here" alt="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab08$@SLASH@$word_sort$@SLASH@$word_vs_list_existing.gif" /> </div> <br /> You might want to make some blocks that operate on words to mirror the following provided list blocks: <br /><br /> <div style="margin-left: 40px;"><img hspace="0" height="126" width="492" vspace="0" border="0" title="There should be an image here" alt="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab08$@SLASH@$word_sort$@SLASH@$word_vs_list_existing_for_list_only.gif" /> </div> Finally, you will probably need to implement the custom blocks that you needed for lists: <br /><br /> <div style="margin-left: 40px;"><img hspace="0" height="126" width="405" vspace="0" border="0" title="There should be an image here" alt="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab08$@SLASH@$word_sort$@SLASH@$word_vs_list_new_blocks.gif" /> </div> <br /> You might also find the block you implemented earlier, which <a href="$@RESOURCEVIEWBYID*8839@$">copies letters</a>, helpful too: <br /><br /> <div style="margin-left: 40px;"> <img hspace="0" height="19" width="208" vspace="0" border="0" title="There should be an image here" alt="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab08$@SLASH@$word_sort$@SLASH@$word_vs_list_helpful.gif" /><br /></div> 1285178581 4026 resource Drawing the board (not the pieces) html

We want to be able to draw rectangles for a board given the number of columns and rows and the range of x and y values that the board should cover. In this step you're going to make the following block that does just that. Notice below that both examples draw in the same range, but there are different numbers of rows and columns in each. <br /><br /> <div style="margin-left: 40px;"><img border="0" width="405" vspace="0" hspace="0" height="26" title="GameBoard" alt="GameBoard" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab05$@SLASH@$GameBoard$@SLASH@$drawBoard48.gif" /><br /></div> <div style="margin-left: 40px;"><img border="0" width="490" vspace="0" hspace="0" height="405" title="There should be an image here" alt="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab08$@SLASH@$gameboard_representation$@SLASH@$Gameboard_4_8.jpg" /><br /></div><br /> <div style="margin-left: 40px;"><img border="0" width="405" vspace="0" hspace="0" height="26" title="Game Board" alt="Game Board" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab05$@SLASH@$GameBoard$@SLASH@$drawBoard84.gif" /><br /></div> <div style="margin-left: 40px;"><img border="0" width="488" vspace="0" hspace="0" height="406" title="There should be an image here" alt="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab08$@SLASH@$gameboard_representation$@SLASH@$GameBoard_8_4.jpg" /><br /></div><br /> <div style="margin-left: 40px;"><br /></div>To do this we needed a helper function to draw a rectangle: <br /> <div style="margin-left: 40px;"><br /></div> <div style="margin-left: 40px;"><img border="0" width="228" vspace="0" hspace="0" height="26" title="Draw rectangle" alt="Draw rectangle" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab05$@SLASH@$GameBoard$@SLASH@$drawRectangle.gif" /><br /><br /></div>The variables that we used to make this were rather complicated. <br /><br />Input to the function:<br /> <ul> <li>width - number of columns desired</li> <li>height - number of rows desired</li> <li>x1 - lower left x position where the board should start</li> <li>y1 - lower left y position where the board should start</li> <li>x2 - upper right x position where the board should start</li> <li>y2 - upper right y position where the board should start</li> </ul>Script variables:<br /> <ul> <li>pixel height - the total number of pixels between x1 and x2<br /></li> <li>pixel width - the total number of pixels between y1 and y2<br /></li> <li>square height - the height (in pixels) of the game board squares<br /></li> <li>square width - the width (in pixels) of the game board squares<br /></li> </ul> <div style="margin-left: 40px;"><img border="0" vspace="0" hspace="0" title="Block Editor" alt="Block Editor" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab05$@SLASH@$GameBoard$@SLASH@$draw_board_block_editor.gif" /><br /><br /></div>Go for it! <br /> 1297281445 4027 resource Homework, Part 1: Common Game Board Actions html

<h1>Homework, Part 1: Common Game Board Actions</h1> <h2>Exercises</h2> This homework exercise deals with <a href="$@RESOURCEVIEWBYID*8836@$">the game board implementation</a> that you created earlier in the lab. Now that we can set pieces in a game board and get pieces from a game board, we can code the following blocks that perform common actions on game boards: <ul> <li><em>Swap</em>: swaps the values at two locations.</li> <li><em>Move</em>: moves the value from one location to another and leaves a blank <tt>B</tt> in the first location.</li> <li><em>Remove</em>: replaces the value with a blank (<tt>B</tt>).</li> <li><em>Drop in column</em>: drops a piece into a column, and works like the game <a href="http://en.wikipedia.org/wiki/Connect_Four">Connect Four</a>, where you can drop a piece into a column. The piece will stop one spot above the first piece it finds. Check out the <a href="http://en.wikipedia.org/wiki/Connect_Four">Wikipedia page for Connect 4</a> to see a picture of this. (<em>Note</em>: It can be a little weird to think about a "column" in a list. We can picture a row as a list item, and a column as the values that are a certain number of spots away from the first values of each row.)</li> </ul> The image below specifies the corresponding blocks and their input types, where <tt>game board</tt> is a list representing a game board. <br /><br /> <div style="margin-left: 40px;"><img border="0" width="328" vspace="0" hspace="0" height="121" title="game moves" alt="game moves" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab06$@SLASH@$GameMoves.jpg" /><br /></div><br /> <div style="margin-left: 40px;"><img border="0" width="256" vspace="0" hspace="0" height="30" title="drop" alt="drop" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab06$@SLASH@$drop.gif" /></div> <br /> For homework, you should implement these blocks. Also, implement error-checking to ensure that the inputs to the blocks are valid. If the user provides invalid inputs to any of the command blocks, then that block should do nothing. For example, if the user were to provide a location to the <tt>Move</tt> block that lay beyond the boundaries of the game board, then the block should do nothing. <h2>Upload and Submit</h2> Once you are done, go to the bSpace site and into the <tt>Assignments</tt> tab. Click on <tt>Homework 05</tt> and upload your BYOB solution<tt></tt>. Once you also upload your solution for <a href="$@RESOURCEVIEWBYID*8851@$">the next section</a>, press <tt>Submit</tt>. 1297281500 4028 resource Homework, Part 2: Make a High-Score List html

<h1>Homework, Part 2: Make a High-Score List</h1> <h2>Exercise</h2> With all that you have learned about lists in this lab and in the previous lab, you are ready to make a high-score list that stores the names and scores of players of a game. The list keeps track of the names of the players and the scores (in order) as shown below. The goal is to write a block that allows you to add a new player to your high-score list. You may find this block useful in later projects. <br /><br /> <div style="margin-left: 40px;"> <img border="0" vspace="0" hspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab07$@SLASH@$Sort$@SLASH@$HighScoreList$@SLASH@$Example.gif" alt="Example of a High-Score list" title="Example of a High-Score list" /></div> <br /> To complete this task, you will make the following blocks that will help you build an abstraction layer. <ul> <li> <tt>Get name from/Get score from</tt>: Instead of always manually accessing the score or the name from a list element, you can write blocks that take a list and an index as inputs and report either the name or score of a player.</li> <li> <tt>Add new score</tt>: This block should add the name provided (<tt>Colleen</tt>) along with the new score (<tt>52</tt>) that is also provided as input. <em>The new score entry should appear in the correct order</em>.</li> </ul> <div style="margin-left: 40px;"> <img border="0" vspace="0" hspace="0" title="Blocks for the High Score List" alt="Blocks for the High Score List" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab07$@SLASH@$Sort$@SLASH@$HighScoreList$@SLASH@$HighScoreListBlocks.gif" /> </div> <h2>Test Cases</h2> As we discussed in previous labs, it is important to test your script on different kinds of input: input that is "regular" or "normal", and input that exercises the "edge cases" of the script. For example, for the <tt>Add New Score</tt> block, we recommend the following test cases: <br /> <ul> <li>Adding a new score to an empty list.</li> <li>Adding a new score that should be placed in the middle of a non-empty list.</li> <li>Adding a new score that should become the highest score in a non-empty list.</li> <li>Adding a new score that should become the lowest score in a non-empty list.</li> <li>Adding a new score that is the same as another score in a non-empty list.</li> </ul> Your homework should include evidence of these tests; you may want to make a different list for each test case. To each test case, attach a comment that describes what is being tested. To make a comment, right-click anywhere on the <tt>Scripts</tt> section and select <tt>add comment</tt>. <div style="margin-left: 40px;"> <img border="0" vspace="0" hspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab07$@SLASH@$Sort$@SLASH@$HighScoreList$@SLASH@$AddComment.png" alt="Adding a Comment" title="Adding a Comment" /></div> BYOB will then provide a pale yellow box where you can add a comment. <div style="margin-left: 40px;"> <img border="0" vspace="0" hspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab07$@SLASH@$Sort$@SLASH@$HighScoreList$@SLASH@$NewComment.png" alt="New Comment" title="New Comment" /></div> Comments are ignored by BYOB, and are mainly meant for us to keep track of our scripts. You can drag these comments around and "attach" them to blocks: <div style="margin-left: 40px;"> <img border="0" vspace="0" hspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab07$@SLASH@$Sort$@SLASH@$HighScoreList$@SLASH@$AttachingComment.png" alt="Attaching a Comment" title="Attaching a Comment" /></div> Once a comment is attached to a block, the comment will follow the block wherever the block is dragged. <div style="margin-left: 40px;"> <img border="0" vspace="0" hspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab07$@SLASH@$Sort$@SLASH@$HighScoreList$@SLASH@$AttachedComment.png" alt="Attached a Comment" title="Attaching a Comment" /></div> <h2>Upload and Submit</h2> Once you are done, go to the bSpace site and into the <tt>Assignments</tt> tab. Click on <tt>Homework 05</tt> and upload your BYOB solution<tt></tt>. Once you also upload your solution for <a href="$@RESOURCEVIEWBYID*8850@$">the previous section</a>, press <tt>Submit</tt>. 1297281654 4029 resource A (Non-Video) Game html

<h1> A (Non-Video) Game </h1>     Let's play a number-guessing game (you have already seen the Scratch version <a href="$@RESOURCEVIEWBYID*8778@$">in lab 3</a>). <br/> <br/>     Between your partner and yourself, decide who will be person G, the guesser: the other person (person P, for picker) picks a number between 1 and 50. Person G asks person P questions to determine the chosen number; the only answers that person P can give are "yes" or "no". The guesser should try two different strategies to playing this game: <br /> <ol> <li>Guessing in sequence: "Is the number 1?", "Is the number 2?", "Is the number 3?", and so on.<br/><br/> </li> <li>Guessing halfway: You know the number must be between 1 and 50, so you start off by asking "Is the number greater than 25?". If the answer is "yes", you instantly know that it must be between 26 and 100, so you ask "Is the number greater than 50?"; otherwise, the number must be between 1 and 25, so you ask "Is the number greater than 12?" Keep asking questions involving the halfway point.</li> </ol>     Play several (around 3) games: person P should pick a wide variety of numbers, while person G should use each strategy alternately. As you play each game, think about which strategy involves fewer questions. Which strategy would be better if, say, the guessing game involved numbers from 1 to 1000? From 1 to a million? Discuss why one strategy better than the other? 1297726884 4030 resource Competing with Young Gauss html

<h1> Competing with Young Gauss </h1> <p>    We would like to add all the numbers from <tt>1</tt> to <tt>N</tt>. One way we can do this is to manually add them, one by one.</p> <p>    We can, however, also follow in the footsteps of the young Johann Carl Friedrich Gauss, a now-revered 18th century mathematician. As the (possibly apocryphal) story goes, he was punished by his elementary school teacher to do the same exercise: add all the numbers from <tt>1</tt> to <tt>100</tt>. The teacher, J. G. Büttner, assumed that the problem would take Gauss a long time to do, yet Gauss finished the problem in a matter of seconds. He realized that, adding <tt>1 + 2 + 3 + ... + 100</tt> was the same as adding <tt>(1 + 100) + (2 + 99) + (3 + 98) + ... + (50 + 51)</tt>. Each pair summed up to <tt>101</tt>, and there were <tt>50</tt> of these pairs, so he quickly deduced that the answer was <tt>101 x 50 = 5050</tt>. </p> <p>    In general, if you wanted to add the numbers from <tt>1</tt> to <tt>N</tt>, the answer would be <tt>(N + 1) * (N/2)</tt>, because there are <tt>(N/2)</tt> pairs, each of which add up to <tt>(N + 1)</tt>.</p> <p>     Imagine that you were playing a game against young Gauss to see who could add numbers from <tt>1</tt> to <tt>N</tt> faster: he does it his way, while you manually add them one by one. You can either win, lose, or tie in this game. What do you think would happen if <tt>N</tt> were <tt>2</tt>? If <tt>N</tt> were <tt>10</tt>? If <tt>N</tt> were <tt>100</tt>? If <tt>N</tt> were a million?</p> 1297727151 4031 resource Time is of the Es-sense html

<h1> Time is of the Es-sense </h1> <p>    We have seen how BYOB can be used to wait for a certain time before reporting anything. BYOB also allows us to do the converse: to report how long a program takes to finish. In the <tt>Sensing</tt> menu, you will see a command called <tt>reset timer</tt> and a reporter called <tt>timer</tt>: <br /> <br /> <div style="margin-left: 40px;"> <img src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab08$@SLASH@$Complexity$@SLASH@$ResetTimer.jpg" alt="Reset Timer Command" title="Reset Timer Command" /> </div> <br />     Activate (tick-mark) the <tt>timer</tt> reporter and you should see a timer ticking away above Alonzo. It's been ticking ever since you opened up BYOB, and counts in tenths of a second:<br/> <div style="margin-left: 40px;"> <img src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab08$@SLASH@$Complexity$@SLASH@$TimerTicking.jpg" alt="Timer ticking away" title="Timer ticking away" /> </div> <br />     We are going to be performing timing experiments in the following sections, so this timer will prove useful. Add the following timing framework script into the space for BYOB scripts:<br/> <div style="margin-left: 40px;"> <img src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab08$@SLASH@$Complexity$@SLASH@$TimingFramework.jpg" alt="Timing Framework" title="Timing Framework" /> </div> <br />     The script will reset the timer whenever the green flag is pressed. Alonzo will then say <tt>Hello!</tt> for 1 second, and soon after that, he will say the current time, less 1 second to account for how long he said <tt>Hello!</tt>. If we replace <tt>Hello!</tt> with a reporter, then Alonzo will say the answer of the reporter, and one second later, how long the reporter took to generate the answer: this is the timing information that we need. Save the script with the name <tt>TimingFramework</tt>. 1297727425 4032 resource Do You Have Time to Add? html

<h1> Do You Have Time to Add? </h1> <p>    Let us start our timing experiments with something simple: how long does it take for a computer to add 1 to (or <em>increment</em>) a number? Replace <tt>Hello!</tt> in the timing script with an addition operator from the <tt>Operators</tt> menu, and add <tt>1</tt> to <tt>100000</tt> (that's five zeros!). Run the script a few times (around four) to get an idea of the average approximate time (in seconds) it takes for the computer to increment <tt>100000</tt>. Run the script repeatedly by double-clicking on it; do <em>not</em> place the script inside a <tt>repeat</tt> or a <tt>repeat until</tt> block, since we are interested in knowing the <em>approximate</em> time the script takes to run once. </p> <p>    Now, pause here and think: what's your gut feeling for how much longer the computer would take if we doubled <tt>100000</tt>? Test your intuition: Get an average approximate time for how long it takes the computer to increment numbers that you progressively double: <tt>200000</tt>, <tt>400000</tt>, <tt>800000</tt>, and <tt>1600000</tt>. Remember that for each number, you need to run the timing script multiple times (around four) to get an idea of the average approximate time (you don't have to be precise). What do you observe? </p> <p>    Take another huge leap and find out how long it (approximately) takes for the computer to increment numbers that you progressively scale by 10: <tt>160000000</tt>, <tt>1600000000</tt> (that's eight zeros), and maybe <tt>16000000000</tt> (that's nine zeros). What do you observe?</p> 1297727516 4033 resource Constant-Time html

<h1>Constant-Time</h1> <p>    In the timing experiments of the previous section, you may have noticed that the computer takes approximately the same time to increment a number, even though the number was made progressively larger. Computer scientists (programmers and theorists) thus call incrementing a number a <strong>constant-time</strong> operation. In fact, <em>any</em> basic arithmetic operation (addition, subtraction, multiplication, division, and exponentiation) is considered to be a constant-time operation.</p> <p>    Notice that we call these operations <em>constant-time</em> operations, but we don't actually say how much time they take. Different computers will take different amounts of time to perform the same operation. To report the exact time of any algorithm, we would have to also report the physical configurations of the computer that the algorithm was run on. This gets very difficult and annoying very fast, especially with the almost infinite variety of computers available today. Instead, we focus on how the running time of an algorithm scales as we scale its inputs to larger and larger sizes, because this is a property of the algorithm itself, and is independent of the computer that it is run on.</p> <p>    Why did the computer take approximately the same amount of time to increment a number, even though that number was getting larger? Think about how you would add one to a number, back from your elementary school days; this is similar to how a computer does its arithmetic (ignoring technical details). The elementary school way of adding numbers goes digit by digit, and so the amount of time it takes for you to add two numbers depends on how many digits each number has. As we doubled the number we were incrementing, we didn't consistently add digits to it, and so the computer took approximately the same time. Even as we began scaling the number by ten, the computer (and you!) takes a relatively really small amount of time to account for the extra digit, so the total time remains approximately constant.</p> <p>    Constant-time operations are the Holy Grail of computer science algorithms, and unfortunately, most algorithms are <em>not</em> constant-time, as we will soon see.</p> 1297727634 4034 resource All the Numbers, All the Time html

<h1>All the Numbers, All the Time</h1> <p>    For this section, we will be using <a href="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab08$@SLASH@$Complexity$@SLASH@$timing.ypr">this timing framework</a>. It is very similar to the framework you constructed earlier, but it also has the stubs for a few blocks that we will be filling in. The first block that we will fill in is already on stage:</p> <div style="margin-left: 40px;"><img title="Insert all numbers between 'start' and 'end' into 'list'" alt="Insert all numbers between 'start' and 'end' into 'list'" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab08$@SLASH@$Complexity$@SLASH@$InsertAllNumbers.jpg" /></div> <p>    This block should fill the input list with all of the numbers from <tt>start</tt> to <tt>end</tt>. If working correctly, the version used on stage should generate all of the numbers from <tt>1</tt> to <tt>max</tt>, where <tt>max</tt> is a number that we will change when running timing experiments, and should add them to the <tt>numbers</tt> list.</p> <p>    First, talk to your partner and discuss an algorithm that you can use to fill the input list with all of the numbers from <tt>start</tt> to <tt>end</tt>. Once you both have decided on an algorithm, complete the body of the block. Now, run the script with <tt>max</tt> set to <tt>10</tt>. Run it a few times to get an idea of the average time the computer takes to generate this list (to the nearest tenth of a second); you don't need to be exact! Repeat the experiment with <tt>max</tt> set to <tt>20</tt>, <tt>40</tt>, <tt>100</tt>, <tt>200</tt>, and <tt>1000</tt>. Do you see a pattern?</p> 1297727701 4035 resource Linear-Time html

<h1>Linear-Time</h1> <p>    You may have noticed that if you increased <tt>max</tt> by a factor of two, then the computer took approximately twice as much time to fill the <tt>numbers</tt> list. Similarly, if you increased <tt>max</tt> by a factor of ten, then the computer took approximately ten times as much time; if you increased <tt>max</tt> by a factor of 100, then the computer ran approximately 100 times longer. In general, as we scale the size of the input by a certain amount, we also scale the running time by the same amount. We call these algorithms <strong>linear-time</strong> algorithms, because if we were to plot the runtime of one such algorithm against the size of its input, we would get a line.</p> <p>    Why is the algorithm a linear-time algorithm? When <tt>max</tt> was set to <tt>20</tt>, we had to add 20 numbers to the <tt>numbers</tt>list; when <tt>max</tt> was set to <tt>40</tt>, we had to add 40 numbers to the number list. In other words, as we scaled <tt>max</tt>, we also scaled how many numbers we had to add to the <tt>numbers</tt> list by the same amount. Linear-time algorithms are also much sought-after in computer science, and for many problems, they are the fastest algorithms you can find.</p> 1297727757 4036 resource Sum-thing's Up html

<h1> Sum-thing's Up </h1> <p> We will now see an example where the runtime of an algorithm really does make a difference. Remember the game you played with young Gauss at the beginning of lab? We will implement the game in BYOB. </p> <p> <a href="$@RESOURCEVIEWBYID*8860@$">Earlier in the lab</a>, you made a block that filled a list with numbers between <tt>1</tt> and <tt>max</tt>. In the <tt>Variables</tt> menu, you will see two blocks:</p> <div style="margin-left: 40px;"> <img src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab08$@SLASH@$Complexity$@SLASH@$AddBlocks.gif" /> </div> <p> The first block sums up the numbers in the <tt>numbers</tt> list the normal, "non-Gauss" way: walking through the list and adding the numbers one by one. The second block sums up the numbers the "Gauss" way: using the formula <tt>(N + 1) * N/2</tt>, where, in this case, <tt>N</tt> is the same as <tt>max</tt>. (<a href="$@RESOURCEVIEWBYID*8854@$">How did we get this formula?</a>) Complete the bodies of these blocks. </p> <p> Once you are done, drag the first block (the "non-Gauss" block) onto the stage and place it immediately after the <tt>add all numbers between 1 and max</tt> block. Also, move the <tt>reset timer</tt> block <em>after</em> the <tt>add all numbers between 1 and max</tt> block, since we only need to time how long the "non-Gauss" block takes to sum the numbers in the <tt>numbers</tt> list.</p> <p> Now, run the script with <tt>max</tt> set to <tt>10</tt>. Again, run it a few times to get an idea of the average time the computer takes to sum the numbers up. Repeat the experiment with <tt>max</tt> set to <tt>20</tt>, <tt>40</tt>, <tt>100</tt>, and <tt>1000</tt>. Based on your observations, what kind of runtime does the "non-Gauss" block have: constant, linear, or neither? Why do you think this is the case?</p> <p> Replace the "non-Gauss" block with the "Gauss" block. Once more, run the script with <tt>max</tt> set to <tt>10</tt>. Again, run it a few times to get an idea of the average time the computer takes to sum the numbers up. Repeat the experiment with <tt>max</tt> set to <tt>20</tt>, <tt>40</tt>, <tt>100</tt>, and <tt>1000</tt>. Based on your observations, what kind of runtime does the "Gauss" block have: constant, linear, or neither? Why do you think this is the case?</p> 1297790124 4037 resource Constant versus Linear html

<h1>Constant versus Linear</h1> <p>    In the experiments in the previous section, we concluded that the "non-Gauss" block had a linear runtime, while the "Gauss" block had a constant runtime.</p> <p>    Both blocks were answering the same question: I have a list of numbers from <tt>1</tt> to <tt>max</tt>, and I want to know what the total of these numbers is. The "non-Gauss" block is a great first attempt at solving the problem, and works rather fast even for large lists. However, its main disadvantage is that its runtime is nonetheless dependent on the length of the input, and so the longer the list, the longer you will have to wait to get an answer. The "Gauss" block, however, does not have to go through the numbers in the list; all it ever needs, every time, is one piece of information: the length of the list, which (in this case) is also the value of <tt>max</tt>. Once you give it this information, it will always perform the same number of arithmetic operations, regardless of whether the list is 10 elements long or 10 million, and that instantly makes it the better algorithm.</p><p>    Many computer scientists work every day to try and get this kind of an improvement in running time, or to try and show that you can't get any faster.</p> 1297726603 4038 resource A Distinct Difference html

<h1>A Distinct Difference</h1> <p> Consider the following problem: I have a list of numbers and I want to know if the numbers in this list are <em>distinct</em>. In other words, I want to know if there are any repetitions in my list. This kind of question pops up frequently in computer science: for example, when returning search results, Google would like to ensure that all of the search results are different from each other (as far as possible). Here is a first attempt at an algorithm (which is a series of steps) to solve the problem:</p> <br /> <strong>Step 1</strong>. I take the first number of the list, and compare it with all of the other numbers in the list (the second number, the third number, and so on). If, at any point, I see the same number again, I stop and tell the user that the numbers are not distinct.<span style="font-weight: bold;"><br /><br /></span> <strong>Step 2</strong>. If I complete step 1 without stopping, I take the second number of the list, and compare it with all of the other numbers in the list (the third number, the fourth number, and so on). If, at any point, I see the same number again, I stop and tell the user that the numbers are not distinct.<span style="font-weight: bold;"><br /><br /></span> <strong>Step 3</strong>. I repeat the two steps above for all of the numbers in the list, each time taking a number from the list and comparing it with all of the following numbers.<br /><br /> <strong>Step 4.</strong> If I am done with all of the numbers in the list, I stop and tell the user that the numbers <em>are</em> distinct. <p> Take a moment to understand the algorithm, and ask any questions that you may have. Using the algorithm above, complete the body of the following block in the <tt>Variables</tt> menu:</p> <br /><br /> <div style="margin-left: 40px;"><img src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab08$@SLASH@$Complexity$@SLASH@$AreDistinctBlock.gif" title="are the numbers in 'list' distinct?" alt="are the numbers in 'list' distinct?" /><br /><br /></div> <p> Once we are done with the block, we need to figure out the <strong>worst-case</strong> running time of the algorithm: how long will this algorithm take on the worst possible input? By "worst", we mean an input that will cause the algorithm to work the most, or to run through the most steps. For this algorithm, for example, what is the worst possible input?</p> <p> Well, since the algorithm only ever stops partway if the numbers in the list are not distinct, we need a list whose numbers are distinct, so that the algorithm will have to look at all the numbers in the list. We already have one such list: the list of numbers from <tt>1</tt> to <tt>max</tt>! (This is turning out to be quite a useful list.) Let's use it!</p> <p> Replace the "Gauss" block from the previous section with the <tt>are the numbers of list distinct?</tt> block that you just made. The list that we are going to test is the <tt>numbers</tt> list, as we explained above. (Also, modify what Alonzo says at the very end of the script to subtract the extra second that he uses to tell us whether the numbers in the list are distinct.)</p> <p> Run the timing script with <tt>max</tt> set to <tt>10</tt>. Again, run the script a few times to get an idea of the average time the computer takes to determine if the numbers in the <tt>numbers</tt> list is distinct.</p> <p> Repeat the experiment with <tt>max</tt> set to <tt>20</tt>, <tt>40</tt>, and <tt>100</tt>. What happens to the running time of the block when the size of the list is doubled? What happens when the size of the list is scaled by a factor of 10? (If you have quite a bit of time, you may want to try and see how long the algorithm takes with <tt>max</tt> set to <tt>1000</tt>.)</p> 1297744512 4039 resource Quadratic-Time html

<h1> Quadratic-Time </h1> <p>    In the timing experiments of the previous section, you may have noticed that the running time of the block increases approximately by a factor of four when the size of the list is doubled; also, the running time increases approximately by a factor of 100 when the size of the list is increased by a factor of ten. In general, as we scale the size of the list by a certain amount, we also scale the running time of the block by the square of that amount. If we were to plot the running time of the block against the size of the list, we would get a parabola or a quadratic function, because as we move along a parabola, any increase in the <tt>x</tt>-coordinate corresponds to a squared increase in the <tt>y</tt>-coordinate. Algorithms similar to that used by this block are thus called <strong>quadratic-time</strong> algorithms. </p> <p>    Why does the algorithm that checks for the distinctness of elements in a list run in quadratic-time? Let's think about how many comparisons we have to do in the worst-case, for a list of length <tt>N</tt>. We compare the first number against <tt>(N - 1)</tt> numbers, the second number against <tt>(N - 2)</tt> numbers, the third number against <tt>(N - 3)</tt> numbers, and so on, until we reach the last number (if we're unlucky), which we have to compare against no other number. In total, we have to do <tt>(N - 1) + (N - 2) + (N - 3) + ... + 2 + 1</tt> total comparisons, which, <a href="$@RESOURCEVIEWBYID*8854@$">according to Gauss</a>, is <tt>[N * (N - 1)]/2</tt> total comparisons, or <tt>(N<sup>2</sup> - N)/2</tt> total comparisons. For large values of <tt>N</tt>, the <tt>N<sup>2</sup></tt> term begins to eclipse the value of <tt>N</tt>:</p> <table width="100%" cellspacing="0" cellpadding="3" border="1" style="font-size: 1em; line-height: inherit; border-collapse: collapse;" id="t5m:"> <tbody> <tr style="text-align: left;"> <td width="20%"><tt>N</tt></td> <td width="20%"><tt>10</tt></td> <td width="20%"><tt>100</tt></td> <td width="20%"><tt>1000</tt></td> <td width="20%"><tt>10000</tt></td> </tr> <tr style="text-align: left;"> <td width="20%"><tt>N<sup>2</sup></tt></td> <td width="20%"><tt>100</tt></td> <td width="20%"><tt>10000</tt></td> <td width="20%"><tt>1000000</tt></td> <td width="20%"><tt>100000000</tt></td> </tr> </tbody> </table> <p>    The difference between <tt>N<sup>2</sup></tt> and <tt>N</tt> is more pronounced for even larger values of <tt>N</tt>. Since we only care about the runtime of algorithms for really large inputs, we say that the contribution of the <tt>N</tt> term is essentially negligible, and that the runtime of the algorithm varies as <tt>N<sup>2</sup></tt>.</p> <p>    You may find the approximation of <tt>(N<sup>2</sup> - N)/2</tt> as <tt>N<sup>2</sup></tt> a bit shocking (mathematicians definitely do); however, in computer science, we make many such approximations because we don't want to drown ourselves in too much detail, and also because this <strong>runtime analysis</strong> is very rough and approximate. The overarching theme of abstraction is evident here: we want to abstract ourselves away from the details of the computer that the algorithm will eventually be run on, and instead gain an idea as to how the runtime of an algorithm will behave for larger and larger inputs.</p> <p>    We would like to answer the question: does the computer get slower for larger inputs on one kind of algorithm than on another? If so, can we make the algorithm faster or better? Answering these questions can sometimes lead to surprising results, as you saw when comparing two different algorithms to sum the numbers in a list.</p> 1297728197 4040 resource Logarithmic-Time html

<h1>Logarithmic-Time</h1> <p>    We will end this lab by introducing another kind of running time that appears frequently when analyzing algorithms. <a href="$@RESOURCEVIEWBYID*8831@$">Two labs ago</a>, we looked at a few ways of finding a number in a list. Earlier in this lab, <a href="$@QUIZVIEWBYID*8862@$">we decided</a> that an algorithm that merely walks through a list to find the number is a linear-time algorithm. (This algorithm, by the way, is fancily known as a <em>linear search</em>. Now you know why.) However, the eternal question: Can we do better?<p> <p>    We also saw an algorithm that worked on sorted lists: we kept dividing the list of numbers into smaller and smaller halves, always looking at the middlemost element to narrow in on the number we are looking for. What is the running time of this algorithm? Well, the runtime is definitely not constant-time, because the longer the list, the more elements we have to look through. However, the runtime is definitely not linear-time either, because we don't ever end up looking at all of the elements of the list. The runtime of this algorithm must lie somewhere in between.</p> <p>    Let's count the number of splits that we have to do for a sorted list of a given size. For a list of size 4, we only ever have to do at most two splits before we find the number we are looking for, or conclude that the number is not in the list. For a list of size 8, after the first split, we are now concerned only with a list of size 4. But, as we have just seen, we only have to do at most two splits before we are done. Again, for a list of size 16, after the first split, we are now concerned only with a list of size 8, which can take three more splits. To summarize:</p> <table width="100%" cellspacing="0" cellpadding="3" border="1" id="t5m:" style="font-size: 1em; line-height: inherit; border-collapse: collapse;"><tbody><tr style="text-align: left;"><td width="20%">Size of list</td><td width="20%"><tt>4</tt></td><td width="20%"><tt>8</tt></td><td width="20%"><tt>16</tt></td><td width="20%"><tt>32</tt></td></tr><tr style="text-align: left;"><td width="20%">Number of splits</td><td width="20%"><tt>2</tt></td><td width="20%"><tt>3</tt></td><td width="20%"><tt>4</tt></td><td width="20%"><tt>5</tt></td></tr></tbody></table> <p>    Notice that when the size of the input doubles, the number of splits (and thus the runtime of the algorithm) increases by one. Also, notice that the top row is growing much faster than the bottom row. This behavior is similar to that of the logarithmic function that you may have seen before, where every multiplicative increase in the input is converted to an additive increase in the output. Such a growth is thus called a <em>logarithmic</em> growth, and this algorithm is a <strong>logarithmic-time</strong> algorithm. (In contrast to the linear search algorithm, this algorithm is known as a <strong>binary search</strong>.)</p> <p>    Logarithmic-time algorithms are also sought-after, since their runtimes are close to, although not quite, constant-time. You can increase the sizes of their inputs by a large factor, yet their running time will increase by a small, <em>added</em> amount, which makes them valuable. In general, any algorithm that involves dividing something into smaller pieces can be a logarithmic-time algorithm.</p> 1297728282 4041 resource View the lab file http://inst.eecs.berkeley.edu/~cs10/fa10/lab/09/

1285957019 4042 resource Scratch Machine Concepts text 2

(display) Scratch supports parallelism! The programming environment is full of concurrency, implicit (two scripts both start when the green flag is clicked, or when they receive the same broadcast message), and explicit (the launch block). Let's first explore the explicit kind, then we'll play with the implicit kind a bit. Let's try to use concurrency for what it was meant for; speed! Three important models of the machine you should develop: The first that Scratch is like a parent with lots of kids, the parent wants to give the kids equal attention. So if there are 3 things happening at one time, Scratch will rotate among the three of them, giving each of them a chance to do their "thing" (e.g., complete one iteration of a loop, say). It will choose the same order every time, in a very predictable way. This is known as time-sharing. The second is that Scratch has a speed governor so that projects run the same speed on different machines. It's obvious why that's important -- imagine developing this great Pac Man game on your parent's slow computer and working very hard to get the timing just right so it's not too fast or slow. However, when you share it with others who have faster machines, it runs too fast to play (because the other computers have a faster "heartbeat", the clock rate). So Scratch slows itself down on faster computers so that it always looks like it's running on the same, slow, computer. The reason this is relevant in the discussion of concurrency is that (on the vast majority of computers) Scratch spends a lot of time just sitting there, waiting, so it has lots of idle "cycles" to handle multiple things running at the same time. The third is that Scratch actually does NOT make use of more than one core (independent hardware computation unit), it runs everything in one core and time shares any parallel task on the single core. This gives Scratch much more control over its parallelism, since once you decide to use two (or more) physical cores, you can no longer control when (or in what order) the computations will return, and you open up the standard Pandora's box of concurrency problems, like deadlock and race conditions. So your Scratch programs are insulated from these realities, allowing you to have predictable parallelism (usually impossible) at the cost of being able to run really fast and make use of hardware resources. 1287171954 4043 resource Scratch Play html

<p align="center"><img height="437" width="181" style="border: medium none;" src="http://inst.eecs.berkeley.edu/%7Ecs10/fa10/lab/09/images/LaunchTutorial.gif" /></p> <ul> <li>(Scratch play) First, to understand the idea of two things happening at once, load up <code><a href="http://inst.eecs.berkeley.edu/%7Ecs10/fa10/lab/09/byob/LaunchTutorial.ypr">LaunchTutorial.ypr</a></code> (shown above). After you click the green flag, let it run for a bit, then hit the space bar once. Then hit it again, and again. Talk with your partner about what is happening, and why. (Answer: When you hit the green flag, Gobo starts off running in a circle, because he's moving and turning at the same time. Now, whenever you hit the space key Gobo's circles become wider because he's moving <em>more</em> than before, and he only does that because his MOVE <em>threads</em> are increasing, not the number of steps per single move. I.e., Scratch initially gives equal time to its 2 "forever" children -- one that turns and one that moves 5 steps. So it's move, turn, move, turn, etc., yielding a (360/15 =) 24-sided polygon with 5-step sides. The next time space bar is pressed, another "child" is born, so now the three equal-time children are: "turn", "move" and "move", yielding a 24-sided polygon with 10-step sides, or a "circle" of twice the size)</li> 1294866493 4044 resource Scratch Debug html

<li>(Scratch debug) When you put two "When green flag ..." hat blocks in the same sprite, both will run at the same time! Similarly, if multiple sprites all have "When green flag..." hat blocks, these will run concurrently as well. Load up <code><a href="http://inst.eecs.berkeley.edu/%7Ecs10/fa10/lab/09/byob/SerialVsParallelBuggy.ypr">SerialVsParallelBuggy.ypr</a></code>, and click the green flag. You'll see one 'serial' gold square 10x10 sprite paint the area on the right by stamping itself. You'll also see two blue 'parallel' 10x10 sprites sharing the labor of painting the area on the left by stamping themselves. Two screenshots are included below, one during computation, and one after all three sprites have finished. <ul> <li>The first thing to note is that the parallel side finished in exactly half the time of the serial side. Discuss with your partner why this is. </li> <li>The second thing to note is that there is a slight concurrency bug. The first blue squares for the 1 and 2 sprites appear not to get stamped. Fix this bug so that there are no missing stamps<code></code>.</li> </ul> </li> <p align="center"><img width="478" height="361" src="http://inst.eecs.berkeley.edu/%7Ecs10/fa10/lab/09/images/ParallelVsSerialStart.png" style="border: medium none;" /> <img width="480" height="361" src="http://inst.eecs.berkeley.edu/%7Ecs10/fa10/lab/09/images/ParallelVsSerialEnd.png" style="border: medium none;" /></p> <ul> </ul> 1297905257 4045 resource Reflection html

It's important to form an accurate mental model of the machine/software when working with it. Hopefully you've seen here that Scratch gives equal time to all the workers (scripts), in lock step, and that concurrency bugs can creep up very easily. 1287172292 4046 resource Overview html

<li>(display) Scratch supports parallelism! Let's explore some of the fun/challenges of concurrent programming, <em>nondeterminism</em>. In this context, this means we can't pre-determine what the results will be; <em>determinism</em> means we <em>could</em> predict what the outputs would be. One of the first exercises we always have parallel programming students do (in other languages) is to have a "dispatcher" start up 10 "workers" (other langauges typically call these <em>threads</em>), numbered 1-10, and all the workers do is shout out "Hello from thread #i" (where i is a number from 1-10). The neat thing that always results is that the result looks something like a random permutation of "Hello from thread #i" numbers, almost never in order. Every time the program runs, a different order comes out. It's neat to see that, and realize when programming concurrently, we need to understand that (for many complicated reasons), the workers may take different amounts of time to return, so our computations shouldn't depend on their order (as the printing example did).</li> 1287172591 4047 resource Scratch Modify html

<li>(Scratch modify) In the last Scratch exercise, it was a little artificial; the sprites were in lock step. Let's take a look at a similar project, <tt><a href="http://inst.eecs.berkeley.edu/%7Ecs10/fa10/lab/09/byob/Determinism.ypr">Determinism.ypr</a></tt>. Here four 60x60 sprites do the same thing (color the screen by stamping themselves through the <code>Fill Screen</code> command shown below), and once they finish, they add their name to the end of the <code>finish</code> variable. Run it a couple of times. Boring, right? That was because Scratch is still in lock step. Make a very small change to Fill Screen - have each sprite wait a random value between 1 and 1/10 seconds before stamping. (this involves the introduction of a very simple command right before the "stamp" call in <code>Fill Screen</code>: "wait (1 / (pick random [1] to [10])) secs"). Run it a few times; now what happens? (Answer: Four "threads" take off, and the slowest (i.e., last) color at each time step is that one who colors that 60x60 square). Save this project as <code>NonDeterminism.ypr</code>.</li> </ul> <p align="center"><img height="188" width="215" alt="FillScreen defintion" src="http://inst.eecs.berkeley.edu/%7Ecs10/fa10/lab/09/images/FillScreen.gif" /><br /> </p> 1287172663 4048 resource Quiz Image html

<ul> <li>(quiz) If we run the following Scratch program and answer "yes", we note that <code>finish</code> is always <tt>123</tt>. What are the possible values of <code>finish</code> if we answer "no"? (we've shown the definition of <code>read and write finish with <em>n</em></code>) </li> </ul> <p align="center"><img height="487" width="1075" style="border: medium none;" src="http://inst.eecs.berkeley.edu/%7Ecs10/fa10/lab/09/images/racecondition.gif" /></p> 1287173385 4049 resource Quiz Answer Explained html

<ul> <li>The answer is: all the permutations of 1,2,3 where all 3 numbers present (= 6) + all the permultations of 1,2,3 where only 2 numbers present (= 6) + all the permutations of 1,2,3 where only 1 number present (=3) for a total of 15 possibilities.</li> <li>If all three numbers present, it's as if we were deterministic. Here's how it could happen (for this example order, obviously all 6 permutations are possible = {123,132,213,231,312,321}): <ul> <li>finish starts empty</li> <li>1 reads finish (), joins its 1, finish is now 1.</li> <li>2 reads finish (1), joins its 2, finish is now 12.</li> <li>3 reads finish (12), joins its 3, finish is now 123.</li> <li>finish is 123</li> </ul> </li> <li>If only two numbers were present, we had a race condition, and here's how it could happen (again, all 6 combinations and permutations are possible = {12,21,13,31,23,32}): <ul> <li>finish starts empty</li> <li>3 reads finish () into its hold</li> <li>1 reads finish () into its hold</li> <li>3 joins its 3 to the number it held (), finish is now 3</li> <li>1 joins its 1 to the number it held () and sets finish to 1. The 3 is now lost, <em>clobbered</em> due to a race condition.</li> <li>2 reads finish (1), joins its 2, finish is now 12.</li> <li>finish is 12</li> </ul> </li> <li>If only one number were present, we also had a race condition, and here's how it could happen (again, all permutations possible = {1,2,3}): <ul> <li>finish starts empty</li> <li>1 reads finish () into its hold</li> <li>2 reads finish () into its hold</li> <li>3 reads finish () into its hold</li> <li>3 joins its 3, finish is now 3</li> <li>2 joins its 2 to the number it held () and sets finish to 2. The 3 is now lost, <em>clobbered</em> due to a race condition.</li> <li>1 joins its 1 to the number it held () and sets finish to 1. The 2 is now lost, <em>clobbered</em> due to a race condition.</li> <li>finish is 1</li> </ul> </li> </ul> 1287173122 4050 resource Scratch Play html

Test your answer by running <code><a href="http://inst.eecs.berkeley.edu/%7Ecs10/fa10/lab/09/byob/RaceCondition.ypr">RaceCondition.ypr</a></code> several times, answering "no". Compare with answering "yes" 1287172906 4051 resource Reflection html

The above problem was an artificial simulation of what happens with other languages which might have three concurrent computations running in hardware, each innocently trying to join their number to the finish line. Thankfully, since Scratch doesn't run separate computations in hardware, this problem doesn't creep up (unless we bend over backwards to do something silly like we do here). Lesson? Whenever possible, make sure your concurrency computations are independent of which worker returns first.</li> 1287173068 4052 resource Overview html

This section is to help you understand the machine model some more, so that you don't get frustrated as you're working on your own projects. There are some subtleties when the same message is broadcast multiple times. 1287173224 4053 resource Scratch Play html

</ul> <p align="center"><img height="655" width="384" style="border: medium none;" src="http://inst.eecs.berkeley.edu/%7Ecs10/fa10/lab/09/images/multiplebroadcast.gif" /></p> <ul> <li> Let's explore some subtle details. <ul> <li>Load in <code><a href="http://inst.eecs.berkeley.edu/%7Ecs10/fa10/lab/09/byob/MultipleBroadcast.ypr">MultipleBroadcast.ypr</a></code>, shown above. <ul> <li>Take a look at the green flag hat block and the "<code>when I receive <em>go</em></code>" hat block Do you agree that all 5 numbers in <code>nums</code> should always be the same when the program is done running? This is called a <em>Loop Invariant</em> (something that if it's true before the loop, will be true after the loop), and it's easy to prove this should always be the case.</li> </ul> </li> <li>Make sure you have "<code>Edit->Thread Safe Scripts</code>" checked.</li> <li>Hit the <code>r</code> key (for <strong>r</strong>eset), space bar (to broadcast <code>go</code> once), <code>w</code> key (to send three consecutive broadcast-and-waits of <code>go</code>), and <code>b</code> key (to send three consecutive broadcasts of <code>go</code>). Are all the values the same? Did you get what you expect? (No, the broadcasts should have incremented each number 3 times but it only incremented it once!)</li> <li>Now uncheck <tt>Edit->Thread Safe Scripts</tt>, and reset the values of all 5 elements to 0.</li> <li>Now reset, and try the <code>space</code>, <code>w</code> and <code>b</code> keys. What just happened? Did you get what you expect? (No, the Broadcasts should have incremented each number 3 times, but it only incremented the first one!)</li> </ul> </li> 1287173284 4054 resource Reflection html

<li>When lots of broadcasts are coming through into a receive block, there are three possibilities: <ul> <li>If you want <em>all</em> of them to take effect, use "<code>broadcast _ and wait</code>"</li> <li>If you don't need all of them to take effect, but want to keep all of your inner data structures consistent, make sure you have <code>Edit->Thread Safe Scripts</code> checked.</li> <li>If you have Edit->Thread Safe Scripts unchecked, you can't trust Scratch to preserve your Loop Invariants!</li> <li>Lesson: The first thing you should always do is check <code>Edit->Thread Safe Scripts</code>! </li> </ul> </li> </ul> 1287173323 4055 resource Recursive Tree Part 1 html

<h1>Recursion</h1> <p>This assignment must be done using the BYOB (Build Your Own Blocks) version of Scratch. <b>When you make blocks, be sure that the ATOMIC box is <u><i>not</i></u> checked! (This will allow you to stop your program if you write a program that will go on forever!)</b> </p> <p>Our goal is to draw a tree like this: <br /></p> <div style="text-align: center;"><img width="246" vspace="0" hspace="0" height="249" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Recurisve_Tree$@SLASH@$nicetree.jpg" alt="There should be an image here" title="There should be an image here" /></div> <div style="text-align: center;"> </div> <p>but we'll start with a simpler version that shows the technique clearly, although less prettily: <br /></p> <p style="text-align: center;"><img width="177" vspace="0" hspace="0" height="191" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Recurisve_Tree$@SLASH@$fulltree.jpg" alt="There should be an image here" title="There should be an image here" /><br /></p> <p>The key to understanding this technique is to see that the tree is a <i>fractal,</i> that is, a picture that contains smaller versions of itself: <br /></p> <p style="text-align: center;"><img width="193" vspace="0" hspace="0" height="205" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Recurisve_Tree$@SLASH@$splittree.jpg" alt="There should be an image here" title="There should be an image here" /><br /></p> <p>We're going to create a TREE block in BYOB Scratch. It'll start with a MOVE block to draw the trunk of the tree, then a TURN block turning left, <i>then a TREE block</i> to draw the left smaller tree, and so on. </p> <p>"Wait!" you're probably thinking. "How can we use a TREE block inside a TREE block? It doesn't exist yet!" That's the big idea for this assignment. </p> <p>We're going to work up to the complicated tree starting with very simple steps. </p> <p>1. Make a TREE1 block (so named because it draws just one level of the tree) using this script: <br /></p> <p style="text-align: center;"><img width="173" vspace="0" hspace="0" height="134" border="0" title="There should be an image here" alt="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Recurisve_Tree$@SLASH@$tree1-script_.jpg" /><br /></p> <p>This looks ridiculously simple, but trust us, it'll get interesting soon. When run, the script draws one tree branch, <i>and then moves the sprite back to its original position.</i> That's going to be really important when we start using scripts within scripts; we always want to be able to assume that our tree blocks leave the sprite in the same position, and facing the same direction, after it as before it. </p> <p>2. Point the sprite facing upward, and put the pen down. Then try TREE1 SIZE 50. You should get a result something like this: <br /></p> <p style="text-align: center;"><img width="57" vspace="0" hspace="0" height="90" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Recurisve_Tree$@SLASH@$tree1.jpg" alt="There should be an image here" title="There should be an image here" /><br /></p> <p>3. Make a TREE2 block that draws two levels: <br /></p> <p style="text-align: center;"><img width="218" vspace="0" hspace="0" height="313" border="0" title="There should be an image here" alt="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Recurisve_Tree$@SLASH@$tree2-script_.jpg" /><br /></p> <p>When run, it should give this result: <br /></p> <p style="text-align: center;"><img width="59" vspace="0" hspace="0" height="116" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Recurisve_Tree$@SLASH@$tree2.jpg" alt="There should be an image here" title="There should be an image here" /></p> <ul> <li>At this rate we'll never be able to make the beautiful version of the tree. In the next step, we'll discuss how to simplify this process. <br /></li> <li>Before going on, make sure that you can mentally trace through the code provided. Paying close attention to the forwards and turns is going to be important to see the big picture and understand the recursion.<br /></li> </ul> 1283356002 4056 resource Recursive Tree Part 2 html

<p>4. That TREE2 block is pretty long and repetitive. But we can simplify it if we notice that in two places it has a move forward/move back pair of blocks, and that this is what TREE1 does! So we can use TREE1 to shorten TREE2. Compare the code below to convince yourself that the new Tree2a will work the same as the original Tree2.<br /></p> <p> <table width="100%" border="1"><tbody> <tr> <td width="33%" valign="top" style="text-align: center;">Tree1<br /> </td> <td width="33%" valign="top" style="text-align: center;">Old Tree2<br /> </td> <td width="33%" valign="top" style="text-align: center;">New Tree2a<br /> </td> </tr> <tr> <td width="33%" valign="top" style="text-align: center;"><img hspace="0" height="134" width="173" vspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Recurisve_Tree$@SLASH@$tree1-script_.jpg" alt="There should be an image here" title="There should be an image here" /><br /> </td> <td width="33%" valign="top" style="text-align: center;"><img hspace="0" height="313" width="218" vspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Recurisve_Tree$@SLASH@$tree2-script_.jpg" alt="There should be an image here" title="There should be an image here" /><br /> </td> <td width="33%" valign="top" style="text-align: center;"><img hspace="0" height="263" width="192" vspace="0" border="0" title="There should be an image here" alt="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Recurisve_Tree$@SLASH@$tree2aS.jpg" /><br /> </td> </tr></tbody> </table><br /></p> <p>Note that the tree blocks inside this TREE2A script are TREE1 blocks, not TREE2 blocks! So there's no mysterious TREE-using-TREE situation here; it's not unusual for one block to be used in another block's script. </p> <p>5. Make a TREE3 block that uses the TREE2 block, on the same pattern, and see if you get the result that you expect. </p> <p>6. If you can stand it, make a TREE4 block that uses the TREE3 block and try it out. </p> <p><b>This would be a good time to save your project.</b> </p> <p>7. Okay, here's the big idea: We can write a TREE block that uses itself in its own script <i>provided that it knows how many levels it's expected to draw!</i> So, in addition to the size input, it'll have a LEVELS input: </p> <p>In the earlier steps, TREE3 used TREE2; TREE2 used TREE1. Here, TREE will use TREE, but reducing the number of levels by 1. </p> <p>8. Once you can draw a tree of five or six levels using your TREE block, see if you can make one like the first picture in this handout. It's different from what we've done so far because the smaller trees are drawn part way up the trunk, instead of at the top of the trunk, and because the pen color is green for the lowest-level branches (the TREE1-like ones) and brown for the others. You don't have to get it exactly like the picture; just try to make a more realistic-looking tree. </p> 1282928114 4057 resource Vary your tree html

Change your tree in the following ways. You should probably try these one at a time so that you can always tell which change you made caused a new bug.<br /> <ul> <li>change the turn angle</li> <li>change the scale factor</li> <li>change the number of recursive calls</li> </ul>Note: If your character goes off the screen your image might get messed up because you'll tell your character to change their y-position but the character literally won't be able to. <br /> 1298518209 4058 resource Random Tree html

We want to make a tree that looks more random. Here are some pictures of different runs of the program with different levels so that you can see what we were thinking.<br /> <div style="text-align: center;"><img hspace="0" height="161" border="0" width="189" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Random_Tree$@SLASH@$Random1.jpg" alt="There should be an image here" title="There should be an image here" /> <img hspace="0" height="162" border="0" width="194" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Random_Tree$@SLASH@$Random2.jpg" alt="There should be an image here" title="There should be an image here" /><img hspace="0" height="164" border="0" width="200" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Random_Tree$@SLASH@$Random3.jpg" alt="There should be an image here" title="There should be an image here" /><br /></div> <div style="text-align: center;"><img hspace="0" height="188" border="0" width="214" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Random_Tree$@SLASH@$Random4a.jpg" alt="There should be an image here" title="There should be an image here" /><img hspace="0" height="189" border="0" width="200" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Random_Tree$@SLASH@$Random5a.jpg" alt="There should be an image here" title="There should be an image here" /><img hspace="0" height="207" border="0" width="206" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Random_Tree$@SLASH@$Random6a.jpg" alt="There should be an image here" title="There should be an image here" /><br /> <div style="text-align: left;">Unfortunately our attempt (shown below) was unsuccessful (see "tree" on the right). Modify the crazy-tree code to produce the random trees as shown above. <br /></div></div><img hspace="0" height="306" border="0" width="330" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Random_Tree$@SLASH@$RandomNotWorkingCode.jpg" alt="There should be an image here" title="There should be an image here" /><img hspace="0" height="186" border="0" width="170" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Random_Tree$@SLASH@$RandomNotWorking.jpg" alt="There should be an image here" title="There should be an image here" /><br /> 1286207981 4059 resource Base Cases html

<div style="text-align: center;"> <div style="text-align: left;">Now that you have some experience with some recursion, we're going to point out some of the anatomy of a recursive procedure.<br /> <ul> <li>We always need a way to figure out that we're done and shouldn't call the recursive call again. Lines 2-4 are the "Base Case" where we handle things that are SO simple we don't need to call the recursive case again.</li> <li>If this isn't the base case we think to ourselves "Woah - That seems complicated. I'll just do a small part of the problem and delegate to someone else". Here's what we do:<br /></li> <ul> <li>draw the trunk of the tree (line 6), <br /></li> <li>position the character for the left sub-tree (line 7), <br /></li> <li>delegate to another copy of the tree block to draw the left sub-tree (line 8), </li> <li>re-position the character for the right sub-tree (line 9),</li> <li>delegate to another copy of the tree block to draw the right sub-tree (line 10),</li> <li>re-position the character to retrace the trunk (line 11), and<br /></li> <li>re-trace the trunk and leave the character exactly where it started out.</li> </ul> </ul>This wasn't the "best" one we discussed in a previous step, but is a good example of a base case. (Note here we addressed the problem of getting infinite recursion when we have a level less than 0.<br /><br /></div><img hspace="0" height="583" border="0" width="574" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Recurisve_Tree$@SLASH@$TreeWithbaseCase.jpg" alt="There should be an image here" title="There should be an image here" /> </div> 1282072153 4060 resource Snowflake html

Using recursion we can make beautiful things! In this step we'll learn to make the beautiful koch snowflake (below)<br /><img border="0" width="380" vspace="0" hspace="0" height="340" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab13$@SLASH@$snowflake$@SLASH@$kochflake.jpg" alt="There should be an image here" title="There should be an image here" /><br />We're going to work with fractals that do not return to the same place between recursive calls. For example, our base case has the character start on the left and go to the right (below). <br /> <div style="margin-left: 40px;"><img border="0" width="339" vspace="0" hspace="0" height="81" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab13$@SLASH@$snowflake$@SLASH@$snow0.gif" alt="There should be an image here" title="There should be an image here" /><br /></div>Then at every successive level, it repeats the previous level 4 times in a pattern shown below. Look at the images below to see how the previous level is repeated in each higher level. <br /> <div style="margin-left: 40px;"><img border="0" width="309" vspace="0" hspace="0" height="106" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab13$@SLASH@$snowflake$@SLASH@$snoww1.gif" alt="There should be an image here" title="There should be an image here" /><br /></div> <div style="margin-left: 40px;"><img border="0" width="309" vspace="0" hspace="0" height="99" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab13$@SLASH@$snowflake$@SLASH@$snoww2.gif" alt="There should be an image here" title="There should be an image here" /><br /></div><br /> <div style="margin-left: 40px;"><img border="0" width="305" vspace="0" hspace="0" height="99" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab13$@SLASH@$snowflake$@SLASH@$snoww3.gif" alt="There should be an image here" title="There should be an image here" /><br /></div><br /> <div style="margin-left: 40px;"><img border="0" width="310" vspace="0" hspace="0" height="102" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab13$@SLASH@$snowflake$@SLASH@$snow4.gif" alt="There should be an image here" title="There should be an image here" /><br /><br /></div>Something that is hard to tell visually is that each recursive call is one-third the size of the previous step. Fill in the blanks in the following recursive function to draw the koch snowflake. Note that at the end of each recursive call we do not end where we started like we did with the trees. <br /><br /> <div style="margin-left: 40px;"><img border="0" width="376" vspace="0" hspace="0" height="306" title="There should be an image here" alt="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab13$@SLASH@$snowflake$@SLASH@$snowflakeFillINBlanks.gif" /><br /></div><br />When you get one side of the snowflake working, combine three of these to actually make the snowflake. <br /> 1298518283 4061 resource C-Curve html

We can make very very complex images by just repeating the same shape multiple times. You'll be writing the recursive function to draw the c-curve. Below our base case is that the character draws a single line. The character starts facing right and faces right at the end (Hint - the direction that the character points at the end is important! It should point in the same direction it did at the beginning of the recursive call).<br /> <div style="margin-left: 40px;"><img width="178" vspace="0" hspace="0" height="48" border="0" title="There should be an image here" alt="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab13$@SLASH@$C-Curve$@SLASH@$ccurve0.gif" /><br /><br /></div>At the next step, we start facing right and end facing right but repeat the previous step twice (red and blue below)<br /> <div style="margin-left: 40px;"><img vspace="0" hspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab13$@SLASH@$C-Curve$@SLASH@$ccurve1.gif" alt="There should be an image here" title="There should be an image here" /><br /></div>At the next step, we start facing right and end facing right but repeat the previous step twice (red and blue below)<br /> <div style="margin-left: 40px;"><br /></div> <div style="margin-left: 40px;"><img vspace="0" hspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab13$@SLASH@$C-Curve$@SLASH@$ccurve2.gif" alt="There should be an image here" title="There should be an image here" /><br /></div><br />At the next step, we start facing right and end facing right but repeat the previous step twice (red and blue below). This continues for each of the next steps, but you should probably focus on the trying to think through the first few steps. Try to make the code work! <br /> <div style="margin-left: 40px;"><br /><img vspace="0" hspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab13$@SLASH@$C-Curve$@SLASH@$ccurve3.gif" alt="There should be an image here" title="There should be an image here" /><br /><br /><img vspace="0" hspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab13$@SLASH@$C-Curve$@SLASH@$ccurve4.gif" alt="There should be an image here" title="There should be an image here" /><br /><br /><img vspace="0" hspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab13$@SLASH@$C-Curve$@SLASH@$ccurve5.gif" alt="There should be an image here" title="There should be an image here" /><br /><br /><img vspace="0" hspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab13$@SLASH@$C-Curve$@SLASH@$ccurve6.gif" alt="There should be an image here" title="There should be an image here" /><br /><br /><img vspace="0" hspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab13$@SLASH@$C-Curve$@SLASH@$ccurve7.gif" alt="There should be an image here" title="There should be an image here" /><br /><br /><img vspace="0" hspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab13$@SLASH@$C-Curve$@SLASH@$ccurve8.gif" alt="There should be an image here" title="There should be an image here" /><br /><br /><img vspace="0" hspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab13$@SLASH@$C-Curve$@SLASH@$ccurve9.gif" alt="There should be an image here" title="There should be an image here" /><br /><br /><img vspace="0" hspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab13$@SLASH@$C-Curve$@SLASH@$ccurve10.gif" alt="There should be an image here" title="There should be an image here" /><br /><br /><img vspace="0" hspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab13$@SLASH@$C-Curve$@SLASH@$ccurve11.gif" alt="There should be an image here" title="There should be an image here" /><br /></div> 1276272141 4062 resource Google "Fractals in Nature" html

Go to Google Image search:<br /><br /><a href=http://www.google.com/images?q=fractals+in+nature" target="_blank">http://www.google.com/images?q=fractals+in+nature</a><br /><br />to search for fractals in nature. There are some beautiful examples of recursive patterns in nature.<br /> <br /> Here is a <a href="http://www.rainbowskill.com/canteen/beautiful-fractals.php">link</a> to a collection of some particularly beautiful fractals occurring in nature. 1279846713 4158 resource Make sure you have filled out the survey html

<h3>A survey!</h3> <p>In order to make this class better <i>and</i> satisfy the funding-powers-that-be, we need you to fill out a short survey. </p> <p>The survey is at <a href="http://www.surveymonkey.com/s/2C7CLFG"> http://www.surveymonkey.com/s/2C7CLFG</a>. </p> <p>Thanks! There will be one more at the end of the course.</p> 1310487419 4063 resource Write countdown using repeats/forever html

<h3>Write countdown using repeats/forever</h3>You have already written countdown that says the numbers from some number (x) to 1. In this lab we're going to write a recursive countdown procedure. Try to write at least two versions of countdown <span style="font-style: italic;">using recursion</span>.<br /> 1286825872 4064 resource Countdown html

We want to make the character count down from any number. Here we're going to discuss how we would write the following block that counts down from a number to zero.<br /><img hspace="0" height="26" border="0" width="197" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Countdown$@SLASH@$call_say_numbers.gif" alt="There should be an image here" title="There should be an image here" /><br /><br />We discussed that we always need a base case. We can think of the base case as when the program is asked to do something SO simple, that it doesn't need to delegate at all. It knows how to do it all by itself. If x is less than 1, we've got that kind of simple case. If x is less than 1 we've decided to just say 0 and be done! <br /> <ul> <li>NOTE: Whenever you write a recursive procedure, make sure you have a base case! Even experienced programmers will forget - so always double-check!<br /></li> </ul><img hspace="0" height="164" border="0" width="284" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Countdown$@SLASH@$SayNumbers_BaseCase.jpg" alt="There should be an image here" title="There should be an image here" /><br /><br />Now we need to figure out what to do next! Say someone gives us a number that isn't less than 1! Say someone gives us the number 13,329,201 - what would we do? <br /><br />"Woah - That seems complicated. I'll just do a small part of the problem and delegate to someone else"<br /><br />So - what we do (below) is say our number (maybe it is 13,329,201) and delegate to a COPY of the function to do the same thing with one number smaller (in our example: 13,329,200).<br /><br /><img hspace="0" height="213" border="0" width="269" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Countdown$@SLASH@$SayNumbers_full.jpg" alt="There should be an image here" title="There should be an image here" /><br /><br /><br /> 1275264192 4065 resource The Non-Recursive Countdown html

You might remember that we could write countdown with a repeat loop. We've included 3 versions of this program so that you can see and begin to feel comfortable with all of these variations. <br /><br /> <div style="text-align: center;"><img hspace="0" height="165" border="0" width="364" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Countdown$@SLASH@$loop1.jpg" alt="There should be an image here" title="There should be an image here" /> <img hspace="0" height="189" border="0" width="367" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Countdown$@SLASH@$Loop2.jpg" alt="There should be an image here" title="There should be an image here" /> <img hspace="0" height="169" border="0" width="360" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Countdown$@SLASH@$Loop3.jpg" alt="There should be an image here" title="There should be an image here" /><br /><br /> <div style="text-align: left;">Next we're going to compare "loop version 1" with our recursive version. Both of these are shown below. <br /><img hspace="0" height="213" border="0" width="269" vspace="0" title="There should be an image here" alt="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Countdown$@SLASH@$SayNumbers_full.jpg" /> <img hspace="0" height="165" border="0" width="364" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Countdown$@SLASH@$loop1.jpg" alt="There should be an image here" title="There should be an image here" /><br /><br /></div> <div style="text-align: left;">We'll discuss representations for how to keep track of what each of these programs does in the next step.<br /><br /></div> </div> 1275271779 4066 resource Tracing a Recursive Function html

What really happens when we call the function below with the argument 3? <br /><img hspace="0" height="26" border="0" width="197" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Tracing$@SLASH@$Recursive_Call_3.gif" alt="There should be an image here" title="There should be an image here" /><br /><br />The flow chart below attempts to show what actually happens! The arrows are numbered to show the sequence of events. We didn't show the sequence of events within each function because we assume you feel comfortable tracing the individual functions.<br /> <ul> <li>The functions have the argument "x" replaced by the actual value.<br /></li> <li>The black arrows show "delegation" to another COPY of the function (i.e. a recursive call)<br /></li> <li>The white arrows show the return of control to the calling function. If the caller had any lines after the recursive call, those would be executed. Later we will work with command blocks, and the white arrow will indicate the recursive call returning a value.<img hspace="0" height="1056" border="0" width="816" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Tracing$@SLASH@$RecursiontraceVersion2.jpg" alt="There should be an image here" title="There should be an image here" /><br /> </li> </ul> 1275277031 4067 resource Tracing a More Complicated Recursive Program html

Below is a small variation to the "say the numbers" program we were just working with. Except this one changed the order of the two lines in the recursive case (see the order of the blocks in the else case). This is more complicated because the function delegates (makes a recursive call) and then when the recursive call returns we still have more blocks to run. Before you start - run this program and compare it to the result of the last program. <br /><br /><img width="258" vspace="0" hspace="0" height="192" border="0" title="There should be an image here" alt="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Countup$@SLASH@$ReverseSayNumber.gif" /><br />The flow chart below attempts to show what actually happens when this new function is called with the argument 3. The arrows are numbered to show the sequence of events. We didn't show the sequence of events within each function because we assume you feel comfortable tracing the individual functions.<br /> <ul> <li>The functions have the argument "x" replaced by the actual value.<br /></li> <li>The black arrows show "delegation" to another COPY of the function (i.e. a recursive call)<br /></li> <li>The white arrows show the return of control to the calling function. The caller had another line after the recursive call, so those are executed at the time indicated by the white arrow. Therefore the numbers will be said in the opposite order! <br /></li> <ul> <li>The first "say" block that is executed is in the COPY of the function where x = 0. <br /></li> <li>Then that function returns to the COPY of the function where x = 1 and we say 1<br /></li> <li>Then that function returns to the COPY of the function where x = 2 and we say 2<br /></li> <li>Then that function returns to the COPY of the function where x = 3 and we say 3<br /></li> </ul> </ul><br /><br /><img width="816" vspace="0" hspace="0" height="1056" border="0" title="There should be an image here" alt="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Countup$@SLASH@$ReversesSayNumber.jpg" /><br /> 1283355914 4068 resource Write a program that says numbers in a range html

Work with your partner to write the following function using recursion. It should say the numbers between x and y (including saying x and y). <span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: 'times new roman'; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; font-size: medium;"><span class="Apple-style-span" style="font-family: verdana,sans-serif; font-size: 12px;"></span></span>For example, when min = 5 and max = 8, your program should print out 5 6 7 8.<br /><br /><img hspace="0" height="56" width="281" vspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab11$@SLASH@$Countup$@SLASH@$FromXtoY.gif" alt="There should be an image here" title="There should be an image here" /><br /><br />Hint: Remember that you'll need a "Base Case" - A case in which the function will not make a recursive call. <br /> 1282923600 4069 resource Make a recursive squiral html

<h3>Make a recursive squiral</h3><br />In a previous lab we made a squiral (shown below.) Make a recursive version of the Squiral block shown below. <br /><br /> <div style="margin-left: 120px;"><img width="171" vspace="0" hspace="0" height="70" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$Squiral$@SLASH@$squiralscript.gif" alt="Script" title="Script" /><br /></div><br /> <div style="margin-left: 120px;"><img width="222" vspace="0" hspace="0" height="222" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$Squiral$@SLASH@$squiralBlock.gif" alt="Block" title="Block" /><br /></div><br /> <div style="margin-left: 80px;"><img width="480" vspace="0" hspace="0" height="360" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$Squiral$@SLASH@$squiral_iamge.gif" alt="Image" title="Image" /><br /></div> 1286837970 4070 resource Example - Square each number html

<h3>Example - Square each number</h3>We've written a block to square each number in a sentence of numbers. The code is available <a href="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$a_recursion_iteration$@SLASH@$squareEachNum.ypr">HERE</a>. We want you to make TWO modifications to the code. <br /> <ul> <li>First - Make the code calculate the cube of each number instead of the square.</li> <li>Second - Make the code reverse the order in which the numbers are shown.<br /></li> </ul><br />Example BEFORE your changes: <br /><img width="427" vspace="0" hspace="0" height="106" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$a_recursion_iteration$@SLASH@$square_each_number.jpg" alt="Square each number" title="Square each number" /><br /><br />Example AFTER your changes:<br /><img width="417" vspace="0" hspace="0" height="102" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$a_recursion_iteration$@SLASH@$CubedReversed.jpg" alt="Cubed and reversed" title="Cubed and reversed" /><br /><br />Code BEFORE your changes:<br /><img width="647" vspace="0" hspace="0" height="553" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$a_recursion_iteration$@SLASH@$Square_each_number_editor.jpg" alt="Editor" title="Editor" /><br /> 1286838005 4071 resource Write a recursive block to add the digits in a number html

<h3>Write a recursive block to add the digits in a number</h3>We have written an iterative (using a loop) version of a block that adds the digits of a number together. For example sum of digits in 12345 is 15. <br /><img width="567" vspace="0" hspace="0" height="431" border="0" title="Sum of digits" alt="Sum of digits" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$a_recursion_iteration$@SLASH@$SumOfDigits.jpg" /><br /><br />Write a recursive version of sum of digits in a number. You will need something similar to the framework below. Fill in the blanks below using blocks from the tools script to make this work like the iterative version above. If you get stuck - the next step has a solution to this problem.<br /><br /><img width="568" vspace="0" hspace="0" height="410" border="0" title="Sum of digits" alt="Sum of digits" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$a_recursion_iteration$@SLASH@$SumOfDigitsRec.jpg" /><br /> 1286838067 4072 resource SOLUTION: recursive block to add the digits in a number html

<h3>Only look at this only if you've tried the last step.</h3><br /><img width="367" vspace="0" hspace="0" height="240" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab04$@SLASH@$a_recursion_iteration$@SLASH@$recursive_sum_of_digits.gif" alt="solution" title="solution" /><br /> 1286838123 4073 resource Recursion in a Nutshell html

<p>We have spent the last couple of labs learning about recursion. This is a resource to summarize what you have learned.</p>

<h1>Recursion in a Nutshell</h1> We have spent the last couple of labs learning about recursion. You have probably realized that the technique for <em>writing</em> recursive blocks is relatively straightforward, although the body of the block can be a bit tricky to figure out until you have gotten enough practice, or have worked through several examples of what the block should do. <br /><br /> When performing recursion, we try to reduce a large problem into a series of similar, smaller problems that can be solved in a similar ways. In fact, it is often best if we can reduce the large problem into a collection of <em>trivially small</em> problems. For example, finding the <a href="http://en.wikipedia.org/wiki/Factorial">factorial</a> of a number is an operation that is often written recursively because each solution builds off of the solution before it (5! = 4! * 5; 12! = 11! * 12). It can be written recursively as a set of trivially small problems (each step only multiplies two numbers) that build up to a significant solution. <br /><br /> <img hspace="0" height="182" width="319" vspace="0" border="0" src="$@FILEPHP@$$@SLASH@$factorial.png" alt="The factorial block in BYOB" title="The factorial block in BYOB" /> <br /><br /> The process for writing recursive functions can be summarized in a few steps: <ol> <li><strong>Determine the <em>base case.</em></strong> The base case is the simplest possible solution to the overall problem. In the example of the factorial, it is simple to find the answer when the number provided is <tt>1</tt>: the answer will always be 1. <em>Every recursive problem has a base case</em> -- sometimes it will be straightforward and other times, it may require a little more thought. What would be the base case for the following recursive problems?<br /> <ul> <li>Searching through a list for the first occurrence of a particular number and replacing it with zero.</li> <li>Counting the number of elements in a list.</li> <li>Computing X<sup>Y</sup>, where X and Y can both be specified as arguments to the block.</li> </ul> <li><strong>Choose a more complicated example.</strong> Continuing our work on the factorial problem, we will consider <img hspace="0" height="35" width="110" vspace="0" border="0" title="Factorial of 10" alt="Factorial of 10" src="$@FILEPHP@$$@SLASH@$factorial_10.png" />. We could choose any number here: 3, 5, 100, 24481, as long as it is not the base case. Hint: sometimes choosing values right next to the base case (2, in this case) makes it harder to detect the relationship in step 3, but any value outside of the base case will do.</li> <li><strong>Consider an example that is <em>slightly simpler</em> (closer to the base case) than the complicated example.</strong> <img hspace="0" height="35" width="103" vspace="0" border="0" title="Factorial of 9" alt="Factorial of 9" src="$@FILEPHP@$$@SLASH@$factorial_9.png" /> might work here. Assuming that we can get the answer to <img hspace="0" height="35" width="103" vspace="0" border="0" title="Factorial of 9" alt="Factorial of 9" src="$@FILEPHP@$$@SLASH@$factorial_9.png" />, how would we use its solution to help us find <img hspace="0" height="35" width="110" vspace="0" border="0" title="Factorial of 10" alt="Factorial of 10" src="$@FILEPHP@$$@SLASH@$factorial_10.png" />? Figuring this out will allow us to determine the "relationship" between solutions, which is a pivotal point in writing a recursive function. In this case, 10! = 9! * 10, which shows a clear relationship that we can represent in BYOB.</li> </ol> 1287382947 4074 resource Practice: Aibohphobia html

This exercise will give you some more practice working with recursion. This time, we are going to use recursion to determine whether a word is a <span style="font-style: italic;">palindrome.</span><br /> <h2>Palindromes</h2>A palindrome is a word or number that is identical when read both forwards and backwards. Most definitions of a palindrome ignore all punctuation, so we will be doing that in our exercise today as well. Some simple palindromes include "kayak," "radar," and "dad," although sentences, poems, and stories can be palindromic as well. For a more complete list, check out <a href="http://www.palindromelist.net/">http://www.palindromelist.net/</a>.<br /> <h2>Exercise</h2>Create a reporter block that has a single argument (a phrase) and returns either true (if the phrase is a palindrome) or false (if the phrase is not a palindrome). Use this block to construct another block that makes Alonzo say one of two things, depending on whether or not the phrase is a palindrome: <br /><br /> <div style="text-align: center;"><img border="0" width="521" vspace="0" hspace="0" height="231" title="Palindromes" alt="Palindromes" src="$@FILEPHP@$$@SLASH@$palindromes.png" /><br /></div><br />There is more than one way to solve this problem, <span style="text-decoration: underline;">but try to accomplish it using recursion</span>. You may want to consider writing a helper block or two to simplify the problem, such as the following (some parts left out):<br /><br /> <div style="text-align: center;"><img border="0" vspace="0" hspace="0" title="Substring in BYOB" alt="Substring in BYOB" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab14$@SLASH@$substring-template.gif" /><br /></div><br /> 1288084698 4075 resource Practice: Adding a range of numbers to a list html

<h1>Adding a Range of Numbers to a List</h1> Lists have an almost unlimited variety of uses and allow us to do a number of things that we could not do otherwise. When dealing with mathematical problems, we can often use lists as "memory" to keep track of numbers that are possible solutions to a problem. A typical example of this sort of situation would involve loading all of the initial possibilities into a list (for example, all of the positive numbers from 1 to 50) and removing items as they are found to be invalid (possibly the numbers that are not evenly divisible by 5, for example). We can continue to remove numbers from the list of possibilities until all of the restrictions have been enforced, leaving only the solutions to the problem in the list. <br /><br /> Write a recursive block that will add all of the numbers between <tt>X</tt> and <tt>Y</tt> (inclusive) to a list. It should be possible to specify the values of <tt>X</tt> and <tt>Y</tt> as parameters to the block, as well as the name of the list that should be affected. <div style="margin-left: 40px;"><img hspace="0" height="40" width="243" vspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab14$@SLASH@$add-numbers.png" alt="Block to add numbers between X and Y to a list" title="Block to add numbers between X and Y to a list" /></div> 1287416339 4076 resource Practice: Performing recursive operations on lists html

After completing the previous exercise you should be able to generate lists of numbers to use for a variety of purposes. Use the block you created in <a href="$@RESOURCEVIEWBYID*8930@$">the previous exercise</a> to test each of these blocks on a variety of numbers. <br /><br /> Create two new recursive blocks. <ul> <li>The first block should remove all numbers below a certain threshold in a list. The block should accept the list and the threshold value as parameters.</li> <li>The second block should reverse the order of all of the elements in a list. The block should accept the list as a parameter.</li> </ul> 1287416407 4077 resource Flood fill html

<h2>Background</h2>"Flood fill" is the name of the technique used by the paint bucket in most graphics programs. It is reasonably easy to implement recursively, and is an example of something that is far simpler to implement recursively than iteratively.<span style="font-style: italic;"></span> The method starts at a particular point in a grid, and spreads in each direction (left, right, up, down) until it reaches a defined barrier of some sort.<br /><br />For example, in Microsoft Paint, when a user clicks on an image with the paint bucket tool, the location of the click will be the starting point, or <span style="font-style: italic;">source</span>, of the flood. The flood will proceed outward from that point in each direction (one direction at a time) <span style="font-style: italic;">unless the space that it would occupy is a different color than the current space</span> (this is the <em>barrier condition</em>). Each point that is colored then attempts to expand into the points surrounding it using the same method.<br /><span style="font-style: italic;"><br /></span> <div style="text-align: center;"><span style="font-style: italic;"><img hspace="0" height="358" width="807" vspace="0" border="0" src="$@FILEPHP@$$@SLASH@$process.png" alt="Fill in a region of an image" title="Fill in a region of an image" /></span><br /><span style="font-style: italic;"></span></div><span style="font-style: italic;"></span><span style="font-style: italic;"><br /></span> <h2>Goal</h2>Using the provided helper blocks, create a recursive block that will update the <span style="font-style: italic;">image</span> grid with the appropriate colors for each cell. Cells should be updated one at a time and the entire image should be redrawn after each cell is updated so that the progress of the flood can be visualized. <br /> <div style="text-align: center; width: 70%; margin: 0pt auto;"><img hspace="0" height="317" width="442" vspace="0" border="0" src="$@FILEPHP@$$@SLASH@$helpers.png" alt="Helper blocks" title="Helper blocks" /> <object height="344" width="425"><param name="movie" value="http://www.youtube.com/v/daXq03ql37o&hl=en&fs=1" /><param name="allowFullScreen" value="true" /><param name="allowscriptaccess" value="always" /><embed height="344" width="425" src="http://www.youtube.com/v/daXq03ql37o&hl=en&fs=1" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" /> </object></div><br />You should <a href="$@FILEPHP@$$@SLASH@$starting_points$@SLASH@$floodfill.ypr">download</a> a set of helper functions that will take care of miscellaneous tasks like drawing, generating a random image, and establishing the image format in a list. You will also be provided with the prototype for a block, <img hspace="0" height="45" width="289" vspace="0" border="0" src="$@FILEPHP@$$@SLASH@$flood-screen.png" alt="Flood block" title="Flood block" />. Provide a body for this block that will start a flood fill and terminate once all of the necessary cells have been filled. The block should be able to start at any red cell in the grid. When called, the block should run until the image has been converted according to the method described above.<br /> <h2>Additional Information</h2><span style="font-weight: bold;">Image Format</span><br /><img hspace="0" height="303" width="165" vspace="0" border="0" src="$@FILEPHP@$$@SLASH@$list.png" style="float: right;" alt="List format" title="List format" />The information for the image is stored in a list, with each element in the list representing a row and each character representing the color of a particular pixel. <br /><br /> <div style="text-align: left;">P = red (a path that the flood can pass through, painting on its way)<br /> </div> W = green (a wall that acts as a barrier for the flood)<br />Y = yellow (a path that's already been visited)<br /><br /> <div style="text-align: center;"> <div style="text-align: left;"><br /></div><br /> <br /></div><span style="font-style: italic;"></span> 1287416512 4078 resource A Prime Opportunity html

Implement a recursive approach to finding prime numbers.<br />

<h2>Background</h2>A <a href="http://en.wikipedia.org/wiki/Prime_numbers">prime number</a> is defined as a natural number that has exactly two distinct natural number divisors (1 and itself). They have a number of mathematical uses, and are also very important to modern encryption techniques.<br /><br /> <div style="text-align: center;"><span style="font-weight: bold;">The First 16 Primes:</span><br /></div><br /> <table border="1" align="middle" width="100%"><tbody> <tr> <td width="25%" valign="top">2<br /> </td> <td width="25%" valign="top">3<br /> </td> <td width="25%" valign="top">5<br /> </td> <td width="25%" valign="top">7<br /> </td> </tr> <tr> <td width="25%" valign="top">11<br /> </td> <td width="25%" valign="top">13<br /> </td> <td width="25%" valign="top">17<br /> </td> <td width="25%" valign="top">19<br /> </td> </tr> <tr> <td width="25%" valign="top">23<br /> </td> <td width="25%" valign="top">29<br /> </td> <td width="25%" valign="top">31<br /> </td> <td width="25%" valign="top">37<br /> </td> </tr> <tr> <td width="25%" valign="top">41<br /> </td> <td width="25%" valign="top">43<br /> </td> <td width="25%" valign="top">47<br /> </td> <td width="25%" valign="top">53<br /> </td> </tr></tbody> </table><br />How can we find prime numbers computationally? The most obvious solution might be to test individual numbers to determine if they are prime by finding the number of factors that they have. Why would this be a non-ideal approach?<br /><br />A Greek mathematician named Eratosthenes came up with a more effective technique long before computers were around. He developed a technique, now called the <a href="http://en.wikipedia.org/wiki/Sieve_of_Eratosthenes">Sieve of Eratosthenes</a> (SoE), around 200 BC. Variations of this technique still rank as one of the most computationally efficient means of generating reasonably small prime numbers. Conveniently for us today, the SoE can be efficiently implemented using recursion!<br /> <h2>The Sieve of Eratosthenes</h2> <p>The Sieve of Eratosthenes is actually a very simple technique from a mathematical standpoint; it approaches the problem of finding factors from the <span style="font-style: italic;">opposite direction</span> than what may seem natural. Instead of finding factors of each individual number, it finds products of individual factors and rules them out as being non-prime numbers. It starts at the smallest prime number, 2, rules out all of the numbers that it divides into evenly (4, 6, 8, 10, etc) and continues up the list of possibilities until all of the non-prime numbers have been removed. Wikipedia has an excellent illustration:<br /></p> <p style="text-align: center;"><img hspace="0" height="445" border="0" width="554" vspace="0" src="$@FILEPHP@$$@SLASH@$Animation_Sieve_of_Eratosthenes.gif" alt="Sieve of Eratosthenes Animation" title="Sieve of Eratosthenes Animation" /><br /></p> <p>Wikipedia also <a href="http://en.wikipedia.org/wiki/Sieve_of_Eratosthenes#Algorithm">outlines the algorithm</a> itself, where <span style="font-style: italic;">n</span> is the highest number under consideration (120 in Wikipedia's illustration) and <span style="font-style: italic;">p</span> is the current prime number (initially 2):</p> <p style="margin-left: 40px;">To find all the prime numbers less than or equal to a given integer <i>n</i> by Eratosthenes' method:</p> <ol style="margin-left: 40px;"> <li>Create a list of consecutive integers from two to <i>n</i>: (2, 3, 4, ..., <i>n</i>).</li> <li>Initially, let <i>p</i> equal 2, the first prime number.</li> <li>Strike from the list all multiples of <i>p</i> less than or equal to <i>n</i>. (<i>2p, 3p, 4p, etc.</i>)</li> <li>Find the first number remaining on the list after <i>p</i> (this number is the next prime); replace <i>p</i> with this number.</li> <li>Repeat steps 3 and 4 until <i>p</i><sup>2</sup> is greater than <i>n</i>.</li> <li>All the remaining numbers in the list are prime.</li> </ol> <h2>Goal</h2>Implement a block labeled "find all prime numbers between X and Y." Here are some important guidelines and rules: <ul> <li>You will need to create multiple types of blocks, including a couple of recursive blocks!</li> <li>The resulting numbers should be stored in a list and displayed on the stage.<br /></li> </ul>This can be an intimidating problem if tackled as a whole. Try breaking it up into multiple sub-problems (one potential sub-problem: filling a list with the numbers from 2 to Y) and solving those individually. Some things to consider:<br /> <ul> <li>Use a list to hold all of the numbers that haven't been ruled out as you process them. Start off by adding all of the numbers between 2 and Y to this list. <br /></li> <li>The sieve technique will only allow you to determine primes between 2 and Y -- you cannot adjust the lower boundary directly. You will have to do this as an additional step.</li> <li>Not <span style="font-style: italic;">every</span> block has to be recursive.<br /></li> </ul> 1278973167 4079 resource Apartment Hunting Throughout the Decades html

Discussion: how would you go about finding and signing a lease on an apartment at college in: 1950, 1990, 2010?<br /><br />What sorts of technological changes have come about in that the past 50 - 80 years that have changed the way that things are done? Consider:<br /> <ul> <li>Travel</li> <li>Financial transactions</li> <li>Communication</li> <li>Search</li> </ul>Problems are <span style="font-style: italic;">constantly</span> being solved by technology, and occasionally new problems are created as well. 1277360240 4080 resource Life Before Search html

<p>Now consider a single cluster of technologies: the Internet and web search. These technologies have only been popular for 20 - 30 years, but its hard to imagine life before them.<br /></p> <h2>Before Search Engines and the Internet<br /></h2>Before the Internet became the phenomenon that it is today, it was considerably more difficult to share information with others, especially if they weren't in the same area of the world. In addition to you and your classmates' submissions in the discussion forum, <a target="_blank" href="http://cybernetnews.com/cybernotes-life-before-the-internet-was-like/"><span class="nolink">CyberNetNews</span></a> mentions a number of differences between then (15 years ago) and now.<br /><br />The Internet today provides a tremendous service of making information available to anyone in the world that can connect to it. "Information" can take the form of company websites, email, instant messaging, audio / video, and many, many other possibilities.<br /> <h2>Early Search Engines</h2>The time of the Internet before search engines was tough as well. The Internet was the same decentralized, wildly diverse collection of information that it is today (although a good bit smaller), but was also terribly difficult to navigate: it was comparable to a telephone network without a phone book. Finding your way to new places on the Internet often involved someone telling you about their site, or stumbling across a site from one you were already familiar with.<br />Not being ones to shy from problems, computer scientists noticed this shortcoming and began working on technology that would automatically <span style="font-style: italic;">crawl</span> and <span style="font-style: italic;">index </span>(more on these later in <a href="$@RESOURCEVIEWBYID*8941@$">How Google Works</a>) the websites that they could find. The directories they created became early search engines. A number of search engines like Lycos, Dogpile, Altavista and Askjeeves used to be big players in the search market. These search engines made huge steps in organizing the Internet by bringing most of it to one place. Nevertheless, the search process was unrefined by modern standards and often required users to search through long lists of sites to find what they needed.<br /><br /> Alas, this wasn't the case for long. Tremendous progress has been made between then and now, much of which has come from a single company that devoted its entire business to search: Google.<br /> <h2>Today's Search</h2>Almost anyone these days is able to find information from across the world in less than half of a second. You can answer almost any question whose solution is known by humanity in under 30 seconds. The amount of information that is available online has taken the world by storm, shifting entire industries and antiquating others. There are tens of millions of websites online at any one time and more are being added every year.<br /><br /> <div style="text-align: center;"><span style="font-weight: bold;">Number of Registered Websites by Month</span><br /></div><br /> <div style="text-align: center;"><img hspace="0" height="300" border="0" width="500" vspace="0" title="Number of web sites" alt="Number of web sites" src="$@FILEPHP@$$@SLASH@$wpid-2009_07_site_count_history.png.gif" /><br /></div><br />If there is so much information available on the Internet, it seems pretty remarkable that today's search engines can come up with such startlingly accurate results for what we want, when we want it.<br /><br /> <div style="text-align: center;"><span style="text-decoration: underline; font-style: italic;">HOW ON EARTH IS THAT POSSIBLE?</span><br /> </div> 1282553629 4081 resource How Google Works html

<h2><span class="nolink">The Problem of Scale</span></h2>One of the hardest parts in the life of a search engine is managing the extraordinary diversity of content it encounters while doing its job (both in the pages it sees and the questions that it gets asked). Instead of trying to do all of the reasoning and analysis when a search term arrives, it tries instead to organize the information in such a way that it learns a little bit about it, and where to find it, before its even asked a question. If search engines were <span style="font-style: italic;">actually</span> going out to every page to look at its content for the first time when you performed a search, it would take forever to get your results. Imagine going to a big concert and being asked to find the oldest person from Indiana at the show. This would be incredibly difficult if you didn't have any information about the people -- but if you were allowed to arrange the people by the origin state as well as their age within each state before the question was asked, then it would become much easier to arrive at a quick and accurate solution. Phone books are alphabetical for a reason!<br /> <h2>The Anatomy of a Search Engine</h2>Search engines, including Google, are generally composed of three major parts: the crawler, the indexer, and the searcher. This video was produced by a team at Google describing how search engines work; listen to their description of the process (they are pretty good at it, after all). Don't worry if you don't follow all of it -- we'll spend more time on it in a second.<br /><br /> <div style="width: 640px; height: 385px; margin: 0pt auto;"> <object height="385" width="640"><param name="movie" value="http://www.youtube.com/v/BNHR6IQJGZs&color1=0xb1b1b1&color2=0xd0d0d0&hl=en_US&feature=player_embedded&fs=1" /><param name="allowFullScreen" value="true" /><param name="allowScriptAccess" value="always" /><embed height="385" width="640" src="http://www.youtube.com/v/BNHR6IQJGZs&color1=0xb1b1b1&color2=0xd0d0d0&hl=en_US&feature=player_embedded&fs=1" type="application/x-shockwave-flash" allowfullscreen="true" allowscriptaccess="always" /> </object></div> <p>Sounds easy enough, right? Today we're going to use BYOB to create a very simple search engine. Search is a reasonably challenging thing to do at all, and an incredibly difficult thing to master (Google, Microsoft, and some others are spending billions trying!). Breaking up the search engine into multiple parts will make the overall problem much more manageable. Understanding the concepts behind search can be challenging, so we'll spend a little bit more time on those in the following section.</p> 1287612741 4082 resource Search Takes a Team html

<h2>Search Takes a Team</h2> <p>The inner workings of search engines are pretty complex systems and can be very intimidating. But what if we were to look at search engines differently? What if we saw them instead as a<span style="font-weight: bold;"> </span><span style="font-weight: bold;">fruit stand</span>?</p> <p style="text-align: center;"><img hspace="0" height="545" border="0" width="800" vspace="0" src="$@FILEPHP@$$@SLASH@$fruit-stand.jpg" alt="Fruit stand" title="Fruit stand" /></p> <p> There may have been a time when this fruit stand could've been run by one person, but now the demand at the stand is far too high for one person and the job is divided up into three different tasks:<br /></p> <p style="margin-left: 40px;"><span style="text-decoration: underline;">Crawler</span>: the task of the Crawler is straightforward: search all of the fields and forests that you can find for fruit. It doesn't matter what kind it is, what it tastes like, or whether you think that anyone will want to eat it. You find it, you take it. The performance of a Crawler could be measured by how much fruit it could gather over time -- the faster the better. Big fruit stands may have multiple crawlers that can easily do their jobs <span style="font-style: italic;">concurrently</span>.<br /></p> <p style="margin-left: 40px;"><span style="text-decoration: underline;">Indexer</span>: the Indexer is the heart of the stand's business. After the Crawler(s) delivers its harvest, the Indexer goes to work organizing the fruit in a way that will be convenient for any Searchers that happen to come by. Depending on the kind of Searchers that the stand typically sees, the Indexer may organize the fruit by type, age, color, size, or otherwise. The cart itself can then be called the <span style="font-style: italic;">index</span>, which is the place where the Indexer places all of the organized fruit. Notice that the word "index" has been used before in this course (in the context of lists as well as loops)...this is the same word but with <span style="text-decoration: underline;">a different meaning</span>! The Indexer puts the fruit on the stand in an order that it can remember so that it can quickly find a particular type of fruit when a Searcher asks for it.<br /></p> <p style="margin-left: 40px;"><span style="text-decoration: underline;">Searcher</span>: the Searcher is the customer who is looking for the perfect fruit. Different Searchers are usually looking for different fruit, and can often be very picky with their requirements for each individual piece. They search through the fruit stand and find the fruit that best fits what they're looking for, and want to get in, find their fruit, and get out as quickly as possible.</p> 1282553909 4083 resource Storing Data for Searching html

<div>Today's goal is going to be to design a simple search engine that can be used to look for words in a list of quotations. We're going to design our search engine similarly to how Google designed theirs (a topic we'll discuss more soon). As you can probably imagine, search engines need to be able to do things <i>quickly</i> in order to be useful, but the techniques we've learned won't give us the speed we need to build a fast search engine. We're going to need something fast -- no, not just fast. <span style="font-style: italic;">L</span><i>ightning</i> fast. <br /></div> <h2>A New Structure: "Hash Tables"</h2> <div style="float: right;"><img hspace="0" height="341" border="0" width="520" vspace="0" src="$@FILEPHP@$$@SLASH@$hash-comparison.png" alt="Hash Comparison" title="Hash Comparison" /></div> <span style="font-weight: bold;">Note: </span>the word <span style="font-style: italic;">index</span> used below has a different meaning than the search engine index that has been used in the rest of the lab.<br /> <br />As you know, lists allow you to store multiple pieces of data in the same variable. You can quickly retrieve the data in a list by providing the <span style="font-style: italic;">index</span> to the data you are trying to find. The index is a number in a list. There is a similar type of data structure, called a <span style="font-style: italic;">hash table</span>, that works very similarly but instead allows you to index using a word or phrase.<span style="font-weight: bold;"></span> You can see the difference between the two storage techniques in the image to the right. Notice that the hash table uses a person's name as the index instead of a number.<br /><br />This is an incredibly powerful data structure for storing data that has relationships with other data. For example, you could implement a phone book using a hash table by using a person's name as the <span style="font-style: italic;">index</span> value and their phone number as the data. When you later needed to find someone's phone number, you could simply provide their name to the hash table to retrieve the data that was associated with it. Today's lab provides three blocks that can be used to easily use a hash table to find information at blazing speeds.<br /><br /><img hspace="0" height="31" border="0" width="210" vspace="0" src="$@FILEPHP@$$@SLASH@$hash-convert.png" alt="Convert to hash table" title="Convert to hash table" /> The first block will allow you to convert a list into a hash table. The first parameter is an empty list and the second is the size of the hash table (i.e. the number of elements you'd like it to hold). After this block finishes, the list that you passed in will be converted into a hash table!<br /><br /> <div style="margin-left: 40px;"><span style="font-weight: bold;">Hint:</span> It's generally better to have about twice as much room in your table as you actually need. Also, for technical reasons, hash tables work best when their size is set to a prime number. You can either set their size as a <a href="http://primes.utm.edu/lists/small/1000.txt">reasonably large prime number</a> or use some other form of determining primes that you may have come up with recently. The prime number that should be used will depend on how much information is being held in the table -- 53 may be good for smaller data sets, while larger projects (such as the final project in this lab) will do better with a size around 521. <br /></div><br /><img hspace="0" height="32" border="0" width="281" vspace="0" src="$@FILEPHP@$$@SLASH@$hash-add.png" alt="Add to table" title="Add to table" /> This block will let you add new information to a hash table. The first parameter gives the entry in the table a name, such as "John Smith" for a phone book. The second parameter is the hash table generated with the help of the first block. The third parameter is the value (a number, phrase, list, whatever) to be associated with John Smith, such as his phone number. This block will insert the information that you specify into the block so that it can be retrieved later.<br /><br /><img hspace="0" height="23" border="0" width="218" vspace="0" src="$@FILEPHP@$$@SLASH@$hash-get.png" alt="Get from table" title="Get from table" /> After you have inserted information, this block will let you quickly retrieve it from the hash table. It will report the value (i.e. the phone number) for the key (i.e. John Smith) that you provide. You must also pass in the hash table generated with the first block.<br /><br /> <div style="clear: both;"> </div> <h2>[Optional] Information for the Curious</h2> <div style="float: right;"><img hspace="0" height="293" border="0" width="300" vspace="0" src="$@FILEPHP@$$@SLASH@$hash-how.png" alt="How a Hash Table Works" title="How a Hash Table Works" /></div> <p>Hash tables are a tremendous tool for a computer scientist's toolbox because they allow for very quick information storage and retrieval. Hash tables make use of two regular lists: one to store the index data, or <span style="font-style: italic;">keys</span>, and the other to store the data, or <span style="font-style: italic;">values</span>. Each key is paired with its own value and entered at equal points in the two lists (see red highlighted region of image). <br /></p> <p>When someone wants to know Cleopatra's phone number, it is then possible to move through the list of keys until Cleopatra's name is discovered, then look up the phone number from the list of values with the equivalent index (if Cleopatra's name is stored in slot 4 of the key list, her phone number will be stored in slot 4 of the values list). In reality, it is not necessary to move through the list in order; there is a special technique called <span style="font-style: italic;">hashing </span>(hence the name 'hash tables') that makes it possible to find elements in far less time.<span style="font-style: italic;"></span> We won't go into the details of that technique here, but the combination of hashing with the two lists is what gives the hash table its power.</p> <p>Feel free to check out the <a href="http://en.wikipedia.org/wiki/Hash_table" title="Hash tables">Wikipedia article on hash tables</a> for more information.<br /></p> 1282629438 4084 resource Practice: Working with Hash Tables html

<h2>Practice</h2> Using <a href="$@FILEPHP@$$@SLASH@$starting_points$@SLASH@$phonebook.ypr">this framework</a>, practice using the hash table functions by building the phone book application mentioned above. You can load all of the data into it that you want, but your tool should allow a user to input someone's name and retrieve their phone number as many times as they like.<br /><br />There are several ways that you could design this application -- what is the best approach that you can think of? Build an application using the blocks below that loads a list of names and phone numbers and then allows a user to look up individual record listings as many times as they would like to.<br /><br /> <div style="text-align: center;"><img hspace="0" height="163" border="0" width="534" vspace="0" src="$@FILEPHP@$$@SLASH@$hash-blocks.png" alt="Hash table blocks" title="Hash table blocks" /><br /> </div> 1287612998 4085 resource Storing Complex Data html

<h2> Improving a Simple Hash Table</h2><img style="float: left; margin: 4px; width: 350px; height: 231px;" alt="Telephone book" src="$@FILEPHP@$$@SLASH@$tbook.jpg" />Hash tables are an incredibly powerful tool for storing data that needs to be accessed quickly. The address book application that you just created can still perform quickly with thousands of people's information stored in it. <br /><br />Are hash tables useful when you need to store more complex information, though? What if you wanted to store multiple pieces of information per key (name), such as multiple phone numbers for the same person? This is simple to do with hash tables as well!<br /><br />Let's say you have to store the home phone number, work phone number, and cell phone number of each person in a list. Knowing how powerful hash tables can be, you would really like to use one to store all of this information. What do <strong>you</strong> think the best way to do this would be? Would your approach only work for phone numbers, or could it be used for many types of complex data?<br /><br />Think about this for a moment -- this will be an important design decision for your search engine, but may be easier to think about in the context of a phone book. Make a note of your idea so that you can use it later in the lab.<br /> 1287613154 4086 resource Searching in BYOB html

And now, the moment you've all been waiting for: it's time to build our search engine!<br /> <h2>Your Job</h2> <p>Your goal is to create a search engine in BYOB that can index and search through a list of quotes. You can download the framework for the search engine <a href="$@FILEPHP@$$@SLASH@$starting_points$@SLASH@$search.ypr">here</a>, which will provide you with the data that your search engine should process as well as some helper functions.</p> <p style="text-align: center;"><img hspace="0" height="262" border="0" width="428" vspace="0" title="Quote search engine" alt="Quote search engine" src="$@FILEPHP@$$@SLASH@$quote-search.png" /><br /></p> <span style="font-weight: bold;">Requirements</span><br style="font-weight: bold;" /> <ol> <li>Start off with the <a href="$@FILEPHP@$$@SLASH@$starting_points$@SLASH@$search.ypr">basic framework</a> provided above.<br /></li> <li><span style="text-decoration: underline;">Crawler</span>. The crawler will be provided to you. It will return a list with a separate source to be analyzed by your search engine in each element.<br /></li> <li><span style="text-decoration: underline;">Indexer</span>. This is where most of the work is going to take place, and where most of the processing time will be spent. Create a keyword index that can be used to quickly determine which quotes contain which words. When the indexer finishes its execution, it should have produced an efficient keyword index that can be used by the Searcher. Use the hash table blocks to store the data in a way that can be searched quickly (perhaps using techniques from earlier in this lab). Remember, multiple quotes may include the same word and you need to be able to locate each quote that contains a search term. Parts of the indexer have been created for you, but you will need to set up the hash table and insert all of the data into it.<br /></li> <li><span style="text-decoration: underline;">Searcher</span>. Add content to the "search for keyword" operator block that can query the index for a particular word and returns a list of all of the quotes that contain that word. The searcher should be able to perform multiple searches on the index without having to regenerate any of the information.<br /></li> <li>Additional requirement: add a special feature to either the indexer or searcher that improves your search engine (either by speeding it up or improving the quality of its results in some way). Be creative! Some ideas:<br /></li> <ol> <li>Rank the returned search results by the number of times the keyword appears in each book. For example, a book that contains the word "fireplace" 12 times would appear before a book that contains the word "fireplace" 5 times.</li> <li>Make it so that your search engine looks for <a href="http://en.wikipedia.org/wiki/Stemming">different forms of the same keyword</a>. One simpler form of this is called suffix stripping; with <a href="http://en.wikipedia.org/wiki/Stemming#Suffix_Stripping_Algorithms">suffix stripping</a>, a search for "player" would also check for words like "play," "played," and "plays."</li> <li>Remove all punctuation from words before inserting them into your index.<br /></li> </ol> </ol> 1287613901 4087 resource Why we simulate html

Computers have, in many ways, given us the ability to explore problems that were utterly out of reach otherwise. One of the most significant of the doors that has been recently opened is the ability to <span style="font-style: italic;">simulate</span> natural events to predict what effects will arise from a particular situation. While pre-simulation science depended on using theories or direct experiments, we are also now able to use theory and mathematical laws to predict things like planet-wide climate change that could not be determined through the use of normal experiments.<br /><br />The scientific community has already incorporated simulation down to the core of some of its projects. From the National Science Foundation's Simulation-Based Engineering Science Report (2006):<br /><br /> <p style="margin: 0pt auto; text-align: center; width: 70%;">"[Scientific simulation] is a discipline indispensable to the nation's continued leadership in science and engineering. It is central to advances in biomedicine, nanomanufacturing, homeland security, microelectronics, energy and environmental sciences, advanced materials, and product development. There is ample evidence that developments in these new disciplines could significantly impact virtually every aspect of human experience." </p><br />Many simulations have a degree of randomness to them to accommodate for the unpredictability of the situations they're trying to represent. Because of this randomness, we can't trust that a single run of a simulation will act as a gateway to the future; instead, we run the simulation many times and determine what the average outcome is. According to the <a href="http://en.wikipedia.org/wiki/Law_of_large_numbers">law of large numbers</a>, if the model that is being simulated is accurate then more trial runs will result in more accurate results. The availability of massive supercomputers today makes it possible to run large simulations many times in a relatively short period of time.<br /> <h2>Recent Examples of Simulation</h2>Simulations already play a pivotal role on many of the frontiers in scientific research today. We have included six major applications of simulations in today's world. Read over any of the examples that seem interesting, in order to get a better feel for what types of problems are typically addressed with techniques like simulation.<br /> 1287953125 4088 resource Climate Change / Global Warming html

<h3>Climate Change / Global Warming</h3> <div style="float: left; margin: 5px;"><img hspace="0" height="312" width="480" vspace="0" border="0" src="$@FILEPHP@$$@SLASH@$105583main1_GlobalWarming_2060_t.jpg" alt="Climate change sim" title="Climate change sim" /></div>Climate change and global warming have been very active topics in recent news and politics. How could we possibly know that the earth is warming, given that we've only been recording atmospheric temperatures for a reasonably short period of time? Using what we've been able to discover about temperature and carbon dioxide levels in the past (experimental evidence) in combination with what we know about sunlight, heat, and the properties of our atmosphere (theory), we are able to create simulators to predict what sorts of temperature trends we will likely see in the future.<br /><br />NASA built one of the most well-known simulators for climate modeling, called the GCM (Global Climate Model). To quote from NASA's website, "A GCM calculates many things, such as how much sunlight is reflected and absorbed by Earth's atmosphere, the temperature of the air and oceans, the distribution of clouds, rainfall, and snow, and what may happen to the polar ice caps in the future." <br /><br />These simulations also allow for the adjustment of variables, like the quantity of CO<sub>2</sub> in the air. Many of the results that have been announced about policy recommendations have stemmed from an understanding of <span style="font-style: italic;">how much </span>we'd have to change, which is data that can only be gathered through simulation. Simulation is hugely helpful in situations like this where we understand many of the subproblems reasonably well (for example, how sunlight reacts when it hits clouds, dense air, or land), but are unable to directly test various routes or solutions to see how they would prevent a particular outcome. 1287953212 4089 resource The Big Bang and the Beginning of the Universe html

<h3>The Big Bang and the Beginning of the Universe<br /></h3> <div style="float: left; margin: 5px;"><img hspace="0" height="312" width="326" vspace="0" border="0" src="$@FILEPHP@$$@SLASH@$lss_chdm.jpg" alt="Universe matter distribution" title="Universe matter distribution" /></div>The world of physics experienced a paradigm shift when Einstein developed his general theory of relativity (all of that E = mc<sup>2</sup> stuff). Einstein, as well as other scientists like James Clerk Maxwell, have led the world of physics into the realization that many of the things that we see can be explained with a very small set of physical rules. In order to test these theories, physics has taken a huge move into the area outside of Earth's atmosphere -- our solar system, galaxy, and universe.<br /><br />Many people (non-scientists included) are intensely curious about the universe. Where did it all come from? How is it possible for life to exist on Earth? Why are there so many stars in the sky? Why aren't there <span style="font-style: italic;">more</span> stars in the sky? These are questions that are not only interesting on a personal level, but also a scientific level to many physicists. Until very recently, it was incredibly difficult to fathom any sort of evidence-based answers to them.<br /><br />Recent improvements in scientific instrumentation, such as satellites and the Hubble Space Telescope, have allowed us to get a much firmer understanding of what our universe is and where it may have come from. However, many of these ideas predict that strange (and possibly invisible, to make matters worse) types of particles and matter must exist in the universe in order for it to have formed in the way it did.<br /><br />That sounds like a serious problem for those who are trying to observe it, but its a perfect application for simulations! Not only are astrophysicists able to predict that it exists, but they can predict about how much of it there should be. Once again, by combining the evidence we've gained from observation with the best physical theories that we have, we are able to simulate what our universe would look like with and without the invisible matter. The simulation above is an image generated by Columbia University showing a possible structure for the universe given that a particular type of this invisible matter actually exists.<br /> 1287953659 4090 resource The Formation of Life on Earth html

<h3>The Formation of Life on Earth<br /></h3>In addition to the question of the origin of the universe, another significant question for many non-scientists is about the origin of life on Earth. Scientists find this to be a very perplexing problem as well, and something that is somewhat difficult to actually perform in the lab due to the very different conditions of a younger Earth. One of the most significant subproblems still to be solved by biologists is to determine the origin of the first DNA, RNA, and amino acids.<br /><br />Within the last few years, scientists have used huge supercomputers to test some of their theories on this idea. Many other parts of the origin of life problem are being examined in similar ways because it's so much easier (and cheaper) to recreate early Earth conditions on a computer than it is in a lab.<br /><br /><a href="http://www.sciencedaily.com/releases/2008/03/080318212430.htm">http://www.sciencedaily.com/releases/2008/03/080318212430.htm</a><br /><a href="http://www.scientificamerican.com/article.cfm?id=can-math-solve-origin-of-life">http://www.scientificamerican.com/article.cfm?id=can-math-solve-origin-of-life</a> <br /> 1282526181 4091 resource Collisions between Galaxies html

<h3>The Collisions of Galaxies</h3> <div style="float: left; margin: 5px;"> <object height="405" width="500"><param value="http://www.youtube.com/v/jexMl2SO6_I&hl=en_US&fs=1?rel=0&border=1" name="movie" /><param value="true" name="allowFullScreen" /><param value="always" name="allowscriptaccess" /><embed height="405" width="500" allowfullscreen="true" allowscriptaccess="always" type="application/x-shockwave-flash" src="http://www.youtube.com/v/jexMl2SO6_I&hl=en_US&fs=1?rel=0&border=1" /> </object></div> Some experiments just seem a bit too dangerous to try. Mixing chemicals can start fires. Testing big weapons can put the lives of many people at risk. But what about colliding two galaxies together? That's taking it to a whole different level, not to mention how difficult this sort of experiment would be to set up given that we have no control over these sorts of things.<br /><br />Nevertheless, our galaxy, the Milky Way galaxy, is expected to collide with the "nearby" Andromeda galaxy in about 3 billion years. What will this mean for both galaxies and anything that happens to inhabit them at that time? Is there any way that studying such a collision could improve our understanding of physics? The video focuses on the Milky Way galaxy as the Andromeda galaxy makes two passes through it: the first is a glancing blow while the second results in a merging of the two into a single galaxy.<br /> 1282526244 4092 resource Space Shuttle / Jet / Car Design html

<h3>Space Shuttle / Jet / Car Design</h3> <div style="float: left; margin: 5px;"><img hspace="0" height="361" width="500" vspace="0" border="0" title="Shuttle aerodynamics" alt="Shuttle aerodynamics" src="$@FILEPHP@$$@SLASH@$gomez.shuttle.jpg" /></div>If you ever work for NASA, here is an easy way to lose your job: build a brand new, high-tech space shuttle without running simulations on it. Don't worry about analyzing how it's going to do in the air -- that's just a waste of time and money. Instead of doing that, we'll just <span style="font-style: italic;">try flying it</span> when it's ready and fix any problems that show up. If things go dreadfully wrong, we'll build another. Don't worry, though, the second one will be <span style="font-style: italic;">much</span> better. So will the third. And the fourth. <br /><br />In the years before computer simulations, this is the route to success that often had to be taken (although not with space shuttles, but perhaps with architecture and bridge building). Success ultimately hinged on the knowledge of the designers and their ability to predict what sorts of conditions the structure would have to tolerate. Today, we're still hinging our success on the same principles, but we're able to predict how a structure will survive <span style="font-style: italic;">far</span> more accurately that we could in the past. We can accurately model wind resistance, temperature change, pressure variation and a multitude of other factors as formulas and calculate them all in a matter of minutes instead of days or weeks. In addition, we're able to try entirely new designs virtually before working with a single piece of real-world material to determine whether a project is worth pursuing or if the design needs to be changed. <br /><br />Why is this so great? <ol> <li>It's possible to do a lot of the planning and testing of a design in a much shorter period of time for much less money than it was in the past.</li> <li>It's possible to see what points of a structure will bear the most stress, and therefore which parts should be reinforced.</li> <li>Adjusting a model is far simpler than rebuilding a real-world prototype.</li> </ol> Software is now available for simulating conditions on buildings, bridges, cars, space shuttles and satellites, and beyond. 1287953948 4093 resource Medical Student Training html

<h3>Medical Student Training</h3> <div style="float: left; margin: 5px;"><img hspace="0" height="300" width="400" vspace="0" border="0" title="Medical simulation" alt="Medical simulation" src="$@FILEPHP@$$@SLASH@$medical.gif" /></div><br />Simulations aren't only useful for discovering new information, but also for spreading knowledge that is already understood by others. In medical school, students are trained to detect and treat huge numbers of problems that occur within the human body. Many times, this often involves using a number of cadavers in order to give the students realistic experiences in their training.<br /><br />One downside of this approach is that the level of participation is limited by the number of cadavers available, especially if the students require cadavers with specific medical illnesses. What if it were possible to have an unlimited number of test subjects with any illness, while still maintaining the level of realism that cadavers provide? Medical training simulations are now gaining popularity that allow for just that. These fake bodies are backed by computers that keep track of pulse rates, respiration rates, and a variety of other bodily functions and provide this data to the students on common medical instruments. It is possible for an instructor to change any of these variables, effectively simulating <span style="font-style: italic;">any physical condition</span> for the students to diagnose and treat. In addition, the fake bodies can be reused as many times as they are needed.<br /> 1282526309 4094 resource Ecosystem Simulation html

<h2>Ecosystem Equilibrium<br /></h2>Natural ecosystems are often incredibly sensitive to change, such as the introduction or removal of a species. A healthy ecosystem is said to be <span style="font-style: italic;">in equilibrium</span>, which is a relatively stable state that keeps population sizes within a sustainable range (not too many of a certain species alive or dead). Consider the case of bears (who only eat fish) and salmon (who are only hunted by bears):<br /> <ul> <li>If the bear population grows particularly large one year, the total population will require more fish to feed it. This will make the salmon population shrink.</li> <li>Over time, if there are fewer salmon, there will not be enough food for all of the bears to eat. Some bears will starve and fewer cubs will be able to prosper, leading to a smaller overall population the next year.</li> <li>As more time passes and the bear population gets smaller, the salmon population will start to increase again due to having fewer natural predators.</li> </ul> <div style="text-align: center;"><img hspace="0" height="512" border="0" width="768" vspace="0" src="$@FILEPHP@$$@SLASH@$Bears-2.jpg" alt="Bears eating Salmon" title="Bears eating Salmon" /><br /></div>In a perfectly stable ecosystem, this cycle can continue indefinitely. Of course, natural ecosystems are <span style="text-decoration: underline;">far</span> more complex than this simple example, but the relationship between species applies to complex ecosystems as well.<br /><br />Because of all of the interdependence between various species, it can be very difficult to understand the implications of small changes to an ecosystem in the real world because (a) the relationships between species can be incredibly complex and (b) actual experimentation in real-world ecosystems can be catastrophic -- by the time observable changes have taken place, it's often too late to stop their effects.<br /><br />Simulations allow scientists and others to determine whether a particular action (such as introducing a non-native species into a habitat) will have unseen effects on a system. Today you will use a simple simulator in Scratch to observe some virtual ecosystems.<br /><br /> <h2>BYOB Simulator</h2> <p>The project we start with today will perform a very simple simulation of a bay (or whatever your favorite shark-infested body of water is) containing sharks and fish. The simulator breaks the ecosystem down into a set of regions in a grid, with each region containing either sharks, fish, or open water. As time goes by, each species behaves by the rules of their <span style="font-style: italic;">population model</span>, which define things like reproduction rates, natural predators, and so on. Sharks have a different set of rules than fish, and each one is adapted for surviving in a different way.<br /></p> <p>The goals for today's lab include:</p> <ul> <li>Check out the population models for the fish and sharks.</li> <li>Change a rule or value of the population model.</li> <li>Create a new species (see below) and insert it into the simulated world. <br /></li> </ul> <p>You can download the simulator <a href="../../file.php/5/starting_points/sharks-fish-simulator.ypr"><strong>here</strong></a>.</p> <p><strong>Step 1: Population Models</strong></p> <p>A <span style="font-style: italic;">population model</span> is just a fancy term for a list of rules that determines how a particular population behaves. The current simulation has two different populations present in it: sharks and fish.</p> <ol> <li>Open the simulator project in BYOB.</li> <li>Notice the two sprites named <tt>Sharks</tt> and <tt>Fish</tt>. Each one of these sprites represents a different population type, and defines the model for the populations behavior on the stage.</li> <li>Click on the Sharks sprite and look at the block attached to the <img hspace="0" height="52" border="0" width="222" vspace="0" src="$@FILEPHP@$$@SLASH@$prepare.png" alt="Prepare Species Hat" title="Prepare Species Hat" /> block. This set of rules defines how the shark population changes over time -- we'll try changing these later. Check out the <tt>Fish</tt> sprite and you'll see that the same block appears there.</li> <li>Run the simulator by clicking on the green flag and wait until the <tt>number of steps</tt> is <tt>10</tt> (note: it may take a long time for the simulator to run). Can you tell that the populations are behaving differently? Make observations but don't worry about recording anything -- you will be asked to make similar modifications later.<br /></li> </ol> <p><strong>Step 2: Manipulating the Models</strong></p> <p>Now that you've seen the models, let's change them all around! We'll change some of the rules in the model so that the populations behave differently.</p> <ol> <li>Click on the <tt>Sharks</tt> sprite and change the <tt>chance of reproduction</tt> to 90% and eliminate the possibility of death by overcrowding.<br /></li> <li>Run the simulator again and observe how the simulation proceeds. Do you notice any differences? Did both species survive for 10 time steps? Again, make observations but don't worry about recording anything.</li> <li>After you've seen the effects of this change, close the project and reopen the original version to restore the original rules.<br /></li> </ol> <p><strong>Step 3: Speciation</strong></p>This simulator was built to be customized, and that is your job today! Your objective is to add a new species to the simulator that will be able to coexist with its neighbor for 25 time steps. Do not change any of the pre-existing population models, but feel free to do whatever you want with yours. There are three steps to creating a new species:<br /> <ol> <li>Duplicate one of the pre-existing sprites (<tt>Sharks</tt> or <tt>Fish</tt>) by right-clicking (option+click on Macs) and clicking <tt>duplicate</tt>. Change the name and icon to represent whatever species you'd like to create.</li> <li>Edit the <img hspace="0" height="29" border="0" width="118" vspace="0" title="Initialize simulator" alt="Initialize simulator" src="$@FILEPHP@$$@SLASH@$initialize-simulator.png" /> block and add an extra <tt>replace</tt> line to the end of the block with your species name as the final argument.</li> <li>Click on your species sprite and change the species name to the same name you used in Step 2. Then change the model as you see fit -- be creative and don't be afraid to experiment! The guidelines provided below may prove useful.</li> </ol><span style="font-style: italic;">When you finish customizing your own species, run the simulator through 25 time steps and save the project. Remember: all three species should survive to the 25th time step.</span><br /> <h2>Simulator Guidelines</h2>Some things that might be helpful to know:<br /> <ol> <li>The chance of reproduction for each species can be adjusted by changing the value of the <tt>chance of reproduction</tt> variable in each sprite. A different rate can be specified for each species type, but every member of the species has the same chance of reproduction (unless you change that in a rule, such as giving a shark who is near fish a higher chance of reproduction).</li> <li>The simulator takes a long time to start up because it is organizing the data in a way that allows the actual time steps to be completed more quickly. You'll have to be patient while it loads.</li> <li>You can create a totally new species by duplicating one of the preexisting species, changing the species name, and adding its new name to the <tt>population types</tt> list in the <tt>World</tt> sprite. Remember to add some members of that species to the initial grid! Look in the <tt>initialize simulator</tt> block to do that.</li> <li>The population model (<tt>rules</tt>) can be assigned by adding new blocks to each species' <tt>rules </tt>list. You can add as many rules as you like. Try reading through the rules -- it should be fairly straightforward what each rule is doing, and comments have been provided as well.</li> </ol> 1288053486 4095 resource Bioinformatics Background file http://bscs.org/pdf/bioinformatics.pdf

Pages 9-44 summarize the basic process

1269723952 4096 resource Background html

One of the key achievements in bioinformatics is the completion of the Human Genome Project. The project aimed to determine the sequence of base pairs in DNA in human beings, with both a goal in identifying the genes and mapping the sequence. The project began in early 1990 and ran until 2003, when a completed draft was published simultaneously by a private group, Celera, and a public group headed by UC Santa Cruz. A number of results have already surfaced, such as identification of various predispositions towards genetic diseases, although much of the interpretation of the data is still to be done.<br><br> While the project encompasses techniques and expertise from a variety of fields, this lab focuses on some computational techniques used to reassemble the DNA sequences. In particular, we will analyze the problem of reassembling DNA during a procedure called shotgun sequencing. In essence, there was no way to sequence an entire chromosome at once. The technique used was to first randomly "cut up" the DNA using restriction enzymes into manageable pieces, and sequencing each of these pieces individually. Where computers came in was in re-assembling each of these small sequences into the original sequence, just like a jigsaw puzzle.<br><br> To get some insight into this problem, take a look at the strips of paper your TA has handed out or will hand out. The idea is that you had originally one long coherent string of DNA. After being cut up, there are now overlapping pieces, and your job is to completely reassemble them. 1271056963 4097 resource Overview html

Now, we'll attack this problem using Scratch. We will assume that these DNA sequences are strings, like any other words we've used in this course. We will start this problem by defining a superstring. A <i>superstring</i> of a set of strings is any string that contains every string in that set. For example, if we had a set RACAD, DABRA, ADABR, ABRAC, ACADA, one possible superstring is RACADABRAADABRABRACACADA. The <i>shortest superstring</i>, is a superstring that is also as short as possible (the solution for the above set is ABRACADABRA).<br /><br /> Basically, we keep combining them, bigger and bigger, like a snowball, until we arrive at the full string. First, we compute overlaps, where ABRA and RACA has 2 overlaps because the RA overlaps. We computer all the pairwise overlaps. We pick the pair with the greatest overlap and combine them into a single string. The above case would have resulted in ABRACA. We repeat this process over and over, until we're left with a single string, which we claim to be the <span style="font-style: italic;">shortest superstring</span>. <br /><br /> 1275950341 4098 resource Substring html

Implement the 'substring' procedure. It should take in a String, and 2 numbers, a start and an end index. 1271102317 4099 resource Overlap html

Given two strings, return the number of overlaps in the shortest common superstring. 1271103346 4100 resource Shortest Common Superstring of 2 Strings html

Write a procedure, that given two text strings, returns the shortest common superstring. 1271103470 4101 resource The Snowball html

Now for the big part of the algorithm! Write a procedure combine, that takes in a list of strings. Your procedure should find the two strings with the most overlap, remove them from the list and combine them into a single string. This string is added back into the list. We continue this procedure until there is only one string left, which it should return. 1271102830 4102 resource Congratulations html

Yay! You've completed an algorithm that will combine many strings in linear time! <br><br> Unfortunately, while this has many parallels to the types of algorithm used in practice, this is somewhat of an oversimplification of the problem. 1271104098 4103 resource How to load the Tools Sprite html

<h3>How to load the Tools Sprite</h3> BYOB comes with a collection of blocks, written in BYOB, that provide commonly useful tools. There are a lot of them, but we're going to concentrate on just a few. These tools can be added to your project by importing the Tools Sprite. (You don't need the sprite itself, but a sprite can be used as a kind of "suitcase" for custom blocks. That's why you're going to import the sprite and then immediately delete it, which seems silly. But deleting the sprite leaves the blocks behind.) <p> This is a short tutorial on how to load it up onto BYOB: <br /> 1) Open the BYOB program </p> <p></p> <div style="text-align: left;"><img border="0" width="119" vspace="0" hspace="0" height="109" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab20$@SLASH@$Lab19-001.png" title="There should be an image here" /></div> <p> 2) Locate your BYOB folder (if you didn't open BYOB from there) and find ToolSprite.ysp. </p> <p></p> <div style="text-align: left;"><img border="0" width="779" vspace="0" hspace="0" height="251" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab20$@SLASH@$Lab19-002.png" title="There should be an image here" /></div> <p> 3) Now simply click and drag ToolSprite.ysp anywhere in the opened BYOB window <br /> 4) You will now see all the new blocks that were imported from the tools sprite in each of the palettes, and you can read the description of each of them if you like in the workspace. After you are done, you can delete the sprite that was created. Hooray! You have successfully installed the tools blocks. </p> <p></p> <div style="text-align: left;"><img border="0" width="341" vspace="0" hspace="0" height="212" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab20$@SLASH@$Lab19-003.png" title="There should be an image here" /></div> <p> </p> <br /> <br /> <b>Here's an alternative way of importing the tools:</b> <p> </p> 1) In BYOB, go to "File" on top and click on "Import Project". <br /> <div style="text-align: left;"><img border="0" width="414" vspace="0" hspace="0" height="184" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19-004.png" title="There should be an image here" /></div> <p> </p> 2) In the "Import Project" window, locate your BYOB folder and find the "tools" file. Click on the file, then press OK. <br /> <div style="text-align: left;"><img border="0" width="539" vspace="0" hspace="0" height="404" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19-005.png" title="There should be an image here" /></div> <p> </p> 4) After checking that the new blocks are in their palettes, delete the tools sprite in bottom right. <div style="text-align: left;"><img border="0" width="341" vspace="0" hspace="0" height="212" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab20$@SLASH@$Lab19-003.png" title="There should be an image here" /></div> 1282601532 4104 resource VIDEO html

<h3>Video<br /></h3><br />Before doing the following lab. Please watch the following video on lists and higher order functions.<br /><br /><br /><a href="http://snap.berkeley.edu/BYOB3-Tutorial2.mov">Click me!</a><br /><br />Note: Some of the blocks in the video may be outdated, but the concepts remain the same.<br /> 1288637683 4105 resource "The Block" html

<h3> The Block </h3> There are two powerful programming ideas we want you to take away from this course. The first is recursion. The second is that program elements — blocks and scripts — can be used as <i>data</i>. You'll see in a moment what that means, and you'll see very shortly why it's a powerful idea. How do we use a block or script as data? If we just put the block or script into our program, it'll be used as an <i>action</i>; that is, BYOB will just perform whatever computation the block or script calls for. We have to <i>encapsulate</i> the block or script, which is a fancy way to say "wrap it up." BYOB provides two "wrapper" blocks, called <b>the block</b> and <b>the script</b>. Right now we're going to work on blocks as data, so we use <b>the block</b>, which you'll find in the Operators menu. <B>The block</b> takes a block as input, and reports the block itself. Compare these two interactions and you'll see what that means: <p><div style="text-align: center;"><img hspace="0" border="0" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$theblock.png" title="THE BLOCK prevents evaluation" /></div> 1282075364 4106 resource "Call" html

<h3> Call </h3> What's the point of turning a block into a datum? It's that <i>eventually</i> we'll want to call the function represented by the block — to run, evaluate, or call the block. (Those words all mean the same thing.) <p>This is where the <b>call</b> block comes in. The <b>call</b> block, which is found in the Control palette, takes an encapsulated block and evaluates it. If we put the block of 1+1 into the <b>call block</b>, 1+1 should now be evaluated and return 2. <p><div style="text-align: center;"><img hspace="0" height="77" border="0" width="237" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab20$@SLASH@$Lab19-02.png" title="There should be an image here" /></div> <p>It's not very interesting to call a block that always does the same thing. We can take a block with <i>unfilled</i> input slots, and <b>call</b> it with the necessary input values provided. To call a block with one or more input values, click the right-facing arrowhead at the end of the <b>call</b> block. Here are some examples: <p><div style="text-align: center;"><img hspace="0" border="0" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$callslots.png" title="CALL of blocks with unfilled slots" /></div> <p>The second example shows that the functions don't have to be <i>arithmetic</i> functions. The third shows that if the block has more than one unfilled slot, and it's called with one input value, then the same value fills all the slots. (We'll see later that you can give more than one input value in a <b>call</b> invocation.) <p>This may still not seem very interesting. Why not just say 8+3, for example, instead of the first example of slot-filling? These capabilities become interesting when we use <i>variables</i> rather than constant inputs, both for the function and for the input slot value. We can write functions of functions, then call the input function with variable data. We're about to see some examples. 1282075399 4107 resource Higher Order Functions html

<h3> Higher Order Functions </h3> <b>Higher Order Functions (HOFs)</b> are "higher order" because they are functions that take another function as an input. Here's a silly example just to show what we mean: The function <b>call-with-5</b> takes a function as input, and reports the value you get by calling that function with the input value 5. You can use any function as the input: <p><div style="text-align: center;"><img hspace="0" border="0" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$callwith5.png" title="example of a HOF" /></div> <p>It turns out that higher order functions are particularly useful along with lists. In this lesson we will mainly use three HOFs that take a function and a list as inputs: <b>Map</b>, <b>Keep</b>, and <b>Combine</b>. They are found in the "Variables" palette, with the other list blocks. Even though we emphasize them, keep in mind that they aren't the only higher order functions; in fact, you can write your own. All of the three main HOFs take a function and a list as inputs, and the function will somehow be applied to the list items. The result varies depending on the the HOF. <p><div style="text-align: center;"><img hspace="0" height="163" border="0" width="299" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19-1.png" title="picture of HOF blocks in palette" /></div> <p>Unlike most of the Scratch list blocks, HOFs are all reporters. If the reported value is a list, it's a newly constructed list; these blocks do <b><i>not</i></b> modify their input lists. This style of programming, in which existing values are not modified, is called <i>functional programming</i>. 1282075422 4108 resource Introduction html

<h3> Using Map </h3> <b>Map</b> takes a reporter block and a list as inputs. It computes a function of each item of the list and report a list of resulting values. The first figure below is an abstract representation of how map would apply to an arbitrary function <b>fn</b>; the others are examples of how to use <b>map</b>. You'll notice that at the left end of the map block is an orange circle containing a number sign. Ignore that for now; it's a rarely-used feature that we'll get back to later. <br /> <div style="text-align: center;"><img hspace="0" height="218" width="352" vspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19-2.png" alt="abstract map block with general function" title="abstract map block with general function" /></div> <p></p> <div style="text-align: center;"><img hspace="0" height="218" width="397" vspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19-24.png" alt="concrete example of map with first-word function" title="concrete example of map with plus function" /></div> <p></p> <div style="text-align: center;"><img hspace="0" height="195" width="500" vspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19-18.png" alt="concrete example of map with first-word function" title="concrete example of map with first-word function" /></div> <p> </p> <br /> <h3> Try these yourself! </h3> Try out the examples above to help you get more familiarized with map, then try these exercises.<br /><br />Make the "first-letters" block that was introduced using map.<br /> <p> </p> Given any list of numbers as an input, use map to add each of those numbers in the list by ten. <p> </p> Given any list of words as an input, use map to to add a letter "s" to the end of those words in the list. 1288637270 4110 resource Transforming the Beatles html

<h3> Transforming the Beatles </h3> Make a "transform-beatles" block that takes a reporter as an argument, applies it to each of the Beatles (John, Paul, George, Ringo), and returns the result in a sentence. Don't forget to use the "list->sentence" block, and <i>make sure you use a list</i> in the script that defines this block. Note that transform-beatles does <i>not</i> take a list or a sentence as an input.<br /> <br /> We can use this to "amazify" the Beatles! <p></p> <div style="text-align: center;"><img border="0" width="627" vspace="0" hspace="0" height="70" title="The transform-beatles block" alt="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19-3.png" /></div> <p></p> <div style="text-align: center;"><img border="0" width="308" vspace="0" hspace="0" height="107" title="The amazify block" alt="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19-4.png" /></div> <p>Hint: First write a version of transform-beatles that reports a <i>list of length four</i> in which each element is one transformed Beatle, then modify the definition to turn the list into sentence form.</p> <h3>Try another problem<br /></h3> <p>Now use your transform-beatles block with an input that will cause it to report the sentence "J P G R" -- the initials of the Beatles. </p> 1282601808 4111 resource Exaggerating your sentences html

<h3> Exaggerating your sentences </h3> Sometimes you might like to exaggerate your statements to make a point. Make an "exaggerate" block which exaggerates sentences. It will double every number that is in the input: <p><div style="text-align: center;"><img hspace="0" height="110" border="0" width="348" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19-8.png" title="There should be an image here" /></div> <p>Your block should also change "good" to "great," "bad" to "terrible," and so on. <p><div style="text-align: center;"><img hspace="0" height="94" border="0" width="487" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19-7.png" title="There should be an image here" /></div> <p> Hint: First make an exaggerate-word block that takes a single <i>word</i> (or number) as input, and reports the exaggerated version of that word. (If it isn't a number or one of the special words like "good," then it doesn't change.) 1282075500 4112 resource Using Keep html

<h3> Using Keep </h3> <b>Keep</b> takes a predicate block and a list as inputs, and reports a new list containing the subset of that list for which the predicate reports TRUE.<br /><br /> <div style="text-align: center;"><img hspace="0" height="77" border="0" width="331" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19-25.png" alt="keep number" title="keep number" /><br /></div> <p></p> <div style="text-align: center;"><img hspace="0" height="193" border="0" width="411" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19-6v2.png" alt="keep number 2" title="keep number 2" /><br /></div> <p></p> <div style="text-align: center;"><img hspace="0" height="213" border="0" width="527" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19-19.png" alt="There should be an image here" title="There should be an image here" /></div> <h3> Try it yourself! </h3> Try out the examples above, then make your own. For example, select all the numbers from a list you make; select words that are four letters long from another list. 1282703659 4113 resource Count "ums" html

<h3> Count "Ums" </h3> When you teach a class, people will get distracted if you say "um" too many times. Make a "count-ums" block that counts the number of times "um" appears in a sentence. <p></p> <div style="text-align: center;"><img hspace="0" height="62" width="366" vspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19-9v2.png" alt="count ums" title="count ums" /><br /></div> 1282715359 4114 resource Choose Beatles html

<h3> Choose Beatles </h3> Make a "choose-beatles" block that takes a predicate block and returns a sentence of just those Beatles (John, Paul, George, and Ringo) that satisfy the predicate. <p></p> <div style="text-align: center;"><img border="0" width="459" vspace="0" hspace="0" height="108" title="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19-10.png" /></div> <p></p> <div style="text-align: center;"><img border="0" width="295" vspace="0" hspace="0" height="125" title="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19-11.png" /><br /> <div style="text-align: left;"><br />Note 1: Your task is to write CHOOSE-BEATLES, not EVEN LENGTH?.<br /><br />Note 2: CHOOSE-BEATLES doesn't take a list of Beatles as input; its only input is the predicate block that specifies which of them to keep in the result.<br /></div></div> 1282602324 4115 resource Using Combine html

<h3> Using Combine </h3> <b>Combine</b> also takes a two-input reporter block and a list as inputs. Combine uses the two-input reporter block to combine items from the list one by one into a single value. For example, the block shown below starts with 4, then computes 4+5=9, then computes 9+6=15.<br /> <p></p> <div style="text-align: center;"><img hspace="0" height="97" width="375" vspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19-12v2.png" alt="using combine" title="using combine" /><br /> <div style="text-align: left;"><br />Note: Unlike MAP and KEEP, COMBINE really makes sense with a small number of reporter blocks as input, because the operation has to be associative (giving the same answer no matter how the operands are grouped). The blocks you'll use often with COMBINE are +, * (but not — or /), MAX, MIN, JOIN, and JOIN WORDS (which is in the tools package).<br /><br /> <h3>Ask Yourself</h3><br />• Why not — or /?<br /><br />• What happens if the input list is empty?<br /><br /></div></div> 1282714934 4116 resource Calculate your GPA html

<h3> Calculate your GPA </h3> You want to calculate your GPA but you're tired of converting the letters to numbers. So you decide to make a GPA block. It takes a sentence of grades and returns the corresponding grade point average. <p></p> <div style="text-align: center;"><img hspace="0" height="64" width="167" vspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19-13v2.png" alt="gpa" title="gpa" /><br /></div> <p> Hint 1: Use "sentence->list" to put the grades in a list that you can use as input to the higher order functions.<br /></p> <p>Hint 2: Make a helper block "base-grade" that takes a single grade as an input and reports 0,1,2,3, or 4, ignoring any plus or minus that might be in the grade, and another helper block "grade-modifier" that takes a single grade as input and reports 0.33, -0.33, or 0 depending on whether the grade has a plus, a minus, or neither. </p> <p></p> <div style="text-align: center;"><img hspace="0" height="64" width="147" vspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19-14v2.png" alt="base-grade" title="base-grade" /><br /><br /><img hspace="0" height="69" width="198" vspace="0" border="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19-15v2.png" alt="grade modifier" title="grade modifier" /><br /></div> <p></p> <div style="text-align: center;"><br /></div> 1282718667 4117 resource Letter Count html

<h3> Letter Count </h3> Make a block "letter-count" that takes a sentence and reports the total number of letters in the words of the sentence (not counting spaces between words). <p></p> <div style="text-align: center;"><img border="0" width="216" vspace="0" hspace="0" height="88" title="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19-16.png" /></div> 1282603480 4118 resource Using Cascade html

<h3> Using Cascade </h3> The cascade block, which is found in the Control palette, takes three inputs: a number, a reporter block, and a starting value (which can be any type). Cascade calls the block with the starting value as input, then calls the block with the value reported the first time, then calls the block with <span style="font-style: italic;">that</span> value, etc., as many times as indicated by the number input.<br /> <p></p> <div style="text-align: center;"><img border="0" width="404" vspace="0" hspace="0" height="140" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19-23.png" title="There should be an image here" /><br /><br /> <div style="text-align: left;">• What happens if the number is zero?<br /><br />• What is 2<sup>15</sup>? (Hint: use 1 as the starting value.)<br /><br />• Make a block that takes a sentence as input and reports the fifth word of that sentence.<br /></div></div> <p> </p> 1288654620 4119 resource Factorials html

<h3> Factorials </h3> Earlier (talking about the MAP block) we promised to explain about the "#" in the orange circle in front of it. CASCADE has one, too, and it means the same thing for both of them: You can drag the # into the reporter block you're using as input to MAP or CASCADE, and it represents how many times the reporter block has been called. So, the first time MAP or CASCADE calls the reporter, # has the value 1; the second time it's 2; and so on. We can use this to compute the product of the numbers from 1 to a given number:<br /> <p></p> <div style="text-align: center;"><img border="0" width="397" vspace="0" hspace="0" height="133" title="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19-20.png" /></div> <p></p> <div style="text-align: center;"><img border="0" width="192" vspace="0" hspace="0" height="88" title="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19-21.png" /><br /><br /></div> The "!" is the mathematical symbol for the <span style="font-style: italic;">factorial</span> function, which is the product of the numbers from 1 to its input.<br /><br /> <div style="text-align: center;">5! = 1x2x3x4x5 = 120<br /></div><br /><br /> 1282604241 4120 resource Finding a Subword html

<h3> Finding a Subword </h3> Make a block "subword" that takes three inputs: a word, a starting position number, and an ending position number. It should report the subword containing only the letters between the specified positions: <p></p> <div style="text-align: center;"><img border="0" width="245" vspace="0" hspace="0" height="99" title="Finding the subword of polythene" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19-22.png" /><br /><br /> <div style="text-align: left;">Hint: Use CASCADE twice.<br /><br /></div></div> 1282604320 4121 resource Important Note! html

<h3>Important Note!</h3> If you have trouble understanding the concepts of HOF's and have not finished the previous lab, please do that first! The following material is a bit more difficult to understand if you are not familiar with HOF's.<br /><br />Also, because this is a HOF lab, <font size="4"><span style="font-weight: bold;">DO NOT</span></font> use recursion, repeat, etc, <span style="font-weight: bold;">anywhere</span>.<br /> 1288832267 4122 resource Introduction html

<h3> Introduction </h3> Now that you've learned about HOF's, we're going to use them for a larger example. We are going to make a program that plays a decent game of tic-tac-toe! Because we are going to be using HOF's, it is natural for us to use lists as our data structure for the game. So first of all, let's make ourselves a board configuration: <p></p> <div style="text-align: center;"><img hspace="0" height="312" border="0" width="179" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19TTT1.png" title="There should be an image here" /></div> <p> </p> <p> We will represent this as a list in BYOB which corresponds with the numbers: I.E. The first item is an underline (which represent a blank square), and the second item is a O. We will call this the <span style="font-weight: bold;">position</span>.<br /></p> <p></p> <div style="text-align: center;"><img hspace="0" height="51" border="0" width="235" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19TTT2.png" title="There should be an image here" /></div> <p> </p> <p>Next, we are going to construct our main block, TTT, which will report the computer's next move given the current configuration. It takes two arguments: the current position and whether the computer is playing X or O. If the computer is O and using the board above, we can use the TTT block like this: </p> <p></p> <div style="text-align: center;"><img hspace="0" height="93" border="0" width="306" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19TTT3.png" title="There should be an image here" /><br /><br /> <div style="text-align: left;"><br />So the computer will go to the first square, which makes sense.<br />Obviously, TTT is not going to work right now because we haven't implemented any strategies yet, nor have we even designed the program structure!<br /></div></div> <p></p> 1288784097 4123 resource Thinking about the Program Structure html

<h3>Thinking about the Program Structure</h3>Remember that this block only represent the strategy in which the computer chooses the next move; we are not programming any visual parts at the moment. <br /><br />Before we approach to make the strategy in BYOB, think about how do you play tic-tac-toe. We have many strategy rules that has priority over another. We will represent these rules with "if" statements:<br /><br /> <ul> <li>If there is a winning move, we take that move.</li> </ul> <ul> <li>If the opponent has a winning move, we move to the square that blocks it.</li> </ul> <ul> <li>If none of the above applies, then choose the best free square.</li> </ul><br />And if you're daring, you may also do this:<br /> <ul> <li>If we can make a move that allows us to win on the next turn, we take that move.</li> <li>If there is a move that the opponent can make that will make them win in two moves, then block it.</li> </ul>The last two allows the computer to play a perfect game of tic-tac-toe.<br /><br />You can see that we are going to make many helper blocks to complete the strategy. We need to check each condition sequentially and make sure we get what we need to get. <br /> 1288784390 4124 resource Triples html

<h3> Triples </h3> When we look at a tic-tac-toe board, we look at each row, column, and diagonal. Essentially the question is "are there three squares in a line that contain two pieces that are mine with one square empty?" In fact nothing really matters about the game besides the potential winning combinations. <p> There are eight winning combinations in tic-tac-toe. By looking at our previous board: </p> <p></p> <div style="text-align: center;"><img hspace="0" height="312" width="179" vspace="0" border="0" title="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19TTT1.png" /></div> <p> We can then make a list of all its winning combinations, or <span style="font-weight: bold;">triples</span> for short. </p> <p></p> <div style="text-align: center;"><img hspace="0" height="152" width="401" vspace="0" border="0" title="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19TTT4.png" /></div> <p> Take a minute to convince yourself that this list is all you need to know about the corresponding board position. Once the strategy finds the triples for a board position, it never needs to look back at the original position again.</p> 1288753375 4125 resource Finding the Triples html

<h3> Finding the Triples </h3> Now we have to convert our first board configuration into the triples we mentioned before. Our program will start with a list of all winning combinations: <p><div style="text-align: center;"><img hspace="0" height="150" border="0" width="406" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19TTT5.png" title="There should be an image here" /></div> <p> and a position such as: <p><div style="text-align: center;"><img hspace="0" height="59" border="0" width="231" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19TTT2.png" title="There should be an image here" /></div> <p> would return: <p><div style="text-align: center;"><img hspace="0" height="152" border="0" width="401" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19TTT4.png" title="There should be an image here" /></div> <p> In order for us to do this, we need to first find a way to "extract" the piece in a specific square. If there is a piece in the square, the piece would be returned, and if there is no piece in the square, the it will return the square back. <p> So first of all, make a <i>substitute-letter</i> block that takes in a square and the position as inputs and returns a piece (X or O) or the square back. <p><div style="text-align: center;"><img hspace="0" height="111" border="0" width="297" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19TTT6.png" title="There should be an image here" /></div> <p> <p><div style="text-align: center;"><img hspace="0" height="95" border="0" width="279" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19TTT7.png" title="There should be an image here" /></div> <p> 1282075953 4126 resource Finding the Triples (Cont') html

<h3> Finding the Triples (Continued) </h3> Next we make a <i>substitute-triple</i> block, which takes one of the eight winning combinations and the position as inputs and returns the winning combination with all the piece "substituted" in. <p></p> <div style="text-align: center;"><img hspace="0" height="203" border="0" width="374" vspace="0" title="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19TTT8.png" /></div> <p> </p> <p></p> <div style="text-align: center;"><img hspace="0" height="201" border="0" width="377" vspace="0" title="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19TTT9.png" /></div> <p> Hint: There is a reason why you made substitute-letter. </p> <p> </p> <p> Lastly, we are going to finish everything up by making the <i>find-triples</i> block. It just takes in a board configuration and returns the list of triples that we wanted. When making this block, it would help if you somehow use the list of 8 winning configurations (1 2 3, 4 5 6.....) and, of course, use substitute-triple. </p> <p></p> <div style="text-align: center;"><img hspace="0" height="69" border="0" width="316" vspace="0" title="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19TTT10.png" /></div> <p> should REPORT something like this: </p> <p></p> <div style="text-align: center;"><img hspace="0" height="267" border="0" width="210" vspace="0" title="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19TTT11.png" /></div> <p>This is ugly, isn't it. Fortunately, we provide a block that helps you read the list.</p> <div style="text-align: center;"><img hspace="0" height="113" border="0" width="386" vspace="0" title="TriplesConverter" alt="TriplesConverter" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab20$@SLASH@$TTT_triples_converter.PNG" /><br /></div><br /> <p style="text-align: center;"><img hspace="0" height="97" border="0" width="584" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab20$@SLASH@$TTT_triples_converter2.PNG" alt="ttt triples converter 2" title="ttt triples converter 2" /><br /></p> <p><br /></p> <p>Beware, triples-converter is <span style="font-weight: bold;">ONLY</span> used to help you read the list; it is not actually used in the program itself!<br /> </p> <p>The entire list should be this: </p> <p></p> <div style="text-align: center;"><img hspace="0" height="152" border="0" width="401" vspace="0" title="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19TTT4.png" /></div> <p> This is exactly how we want it! </p> 1290929323 4127 resource Can the Computer Win on this Move? html

<h3> Can the Computer Win on this Move? </h3> So because we are able to convert our board into triples, we can make a block that detects the computer's winning move. <p> <p> <br> Now make a helper block called appearances that takes any inputs and return the number of times the input is an element in the list. <p><div style="text-align: center;"><img hspace="0" height="76" border="0" width="253" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19TTT12.png" title="There should be an image here" /></div> <p> We can use this block to detect how many pieces we have in a winning combination. Using the appearances block, we can make the my-pair block (which is provided below) that takes in a winning triple and your piece as inputs. <p><div style="text-align: center;"><img hspace="0" height="132" border="0" width="389" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19TTT13.png" title="There should be an image here" /></div> <p> <p><div style="text-align: center;"><img hspace="0" height="146" border="0" width="180" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19TTT14.png" title="There should be an image here" /></div> <p> The block returns <i>true</i> if there is two of your pieces in a winning triple AND if your opponent do not have a piece in the same winning triple. (Meaning that your piece can win!) <p><div style="text-align: center;"><img hspace="0" height="74" border="0" width="260" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19TTT15.png" title="There should be an image here" /></div> <p> The block should return <i>false</i>, otherwise. <p><div style="text-align: center;"><img hspace="0" height="69" border="0" width="268" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19TTT16.png" title="There should be an image here" /></div> <p> 1282076000 4128 resource Can the Computer Win on this Move? (Cont') html

<h3> Can the Computer Win on this Move? (Continued) </h3> With the my-pair? block, you can make the first version of the <i>i-can-win? block.</i> This block should take in two inputs: a list of triples and a piece, and should return true if there is one or more triple that contains your winning move. <p></p> <div style="text-align: center;"><img hspace="0" height="183" border="0" width="445" vspace="0" title="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19TTT17.png" /></div> <p> </p> <p></p> <div style="text-align: center;"><img hspace="0" height="179" border="0" width="448" vspace="0" title="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19TTT18.png" /></div> <p> Okay, now we knowing that there is a winning move for the computer, but knowing that there is a winning move isn't much help unless we know where it is. Modify the i-can-win? block so that if there is a winning move, return the square. <br /> <br /> It would also help if you wrote a <i>choose-win?</i> block that takes in the <span style="font-style: italic;">winning triples</span> and returns false if the given input is an empty list - otherwise it returns back the winning square (a number, NOT A LIST). </p> <p></p> <div style="text-align: center;"><img hspace="0" height="180" border="0" width="419" vspace="0" title="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19TTT19.png" /></div> <p> </p> 1288819675 4129 resource Blocking the Opponent html

<h3>Blocking the Opponent</h3> Now that you've made a block to allow the computer to win, you must now make a block to block the computer's opponent winning move. You made something like this before! You don't have to go through the complicated process of finding triples that have two of the opponent's letter piece and none of the computer's piece - it's already done for one way. <br /> <br /> By using the i-can-win? block, make a <i>opponent-can-win?</i> block that takes a list of triples and a piece as inputs and returns the square that the computer should block. If there isn't, return false. <p></p> <div style="text-align: center;"><img width="443" vspace="0" hspace="0" height="169" border="0" title="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19TTT20.png" /></div> <p> </p> <p></p> <div style="text-align: center;"><img width="428" vspace="0" hspace="0" height="178" border="0" title="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$Lab19TTT21.png" /></div> <p></p> 1288679100 4130 resource Best Free Square html

<h3>Best Free Square<br /></h3>There won't always be a move where you can win or block an opponent's winning move. So now we want to make sure that the computer will take the best free square. For example, it's always good to take the middle square (5) first when playing the game; if that's taken, then you take one of the corners. Make the <span style="font-style: italic;">best-free-square </span>block that takes in a triple as the input and returns the best move for the computer.<br /><br /> <div style="text-align: center;"><img hspace="0" height="77" border="0" width="338" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab20$@SLASH@$TTT_bestfreesquare.PNG" alt="bestfreesquare" title="bestfreesquare" /><br /><br /> <div style="text-align: left;">It would be very helpful if you also made a helper block for best-free-square that would search inside the triples and see whether or not the preferred square is available.<br /></div></div> 1288783560 4131 resource Finishing Up html

<h3>Finishing Up</h3>So we made our three main strategy blocks: one to take the winning move, one to block the opponent's winning move, and one to take the best free square. Now that we have our three primary strategies for the computer, it's time to put them all together.<br /><br />Make the block <span style="font-style: italic;">ttt-choose</span>, which the main block, <span style="font-style: italic;">ttt</span>, will contain, that goes through each strategy. If a strategy does not return false, then the computer should use that strategy to make its next move. ttt-choose takes in two inputs, triples and the computer's piece. (X or O). It should return the best move.<br /><br /> <div style="text-align: center;"><img hspace="0" height="169" border="0" width="394" vspace="0" title="ttt-choose" alt="ttt-choose" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$TTT_tttchoose.PNG" /><br /><br /></div>Then we can finish ttt, which takes in a position as an input and the computer's piece. As stated before, ttt would contain the ttt-choose block, so the <span style="font-style: italic;"><span style="font-style: italic;"><span style="font-style: italic;"></span></span>find-triples</span> will be helpful.<br /><br /> <div style="text-align: center;"><img hspace="0" height="63" border="0" width="311" vspace="0" title="ttt" alt="ttt" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab19$@SLASH@$TTT_ttt.PNG" /><br /></div><br /> 1288786359 4132 resource Final Comments and Optional Exercises html

<h3>Final Comments and Optional Exercises</h3>You may have noticed that you didn't make the entire Tic-Tac-Toe program; we only made a strategy that a computer would use when given the position. Therefore, when the computer gives back a move, the position is never updated. There is also no interaction between the user and the computer.<br /><br />If you like (or if you have time), you can implement this interaction between the user and the computer, and include any fancy visuals in BYOB.<br /><br /> <div style="text-align: center;"><img hspace="0" height="372" border="0" width="499" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab20$@SLASH@$TTT_visual.PNG" alt="tttvisual" title="tttvisual" /><br /><br /></div>Also, the tic-tac-toe strategy that we implemented is not perfect either. Think about the last two strategy that were mentioned earlier:<br /> <ul> <li>If we can make a move that allows us to win on the next turn, we take that move.</li> </ul> <ul> <li>If there is a move that the opponent can make that will make them win in two moves, then block it</li> </ul>Including these two would make the program play tic-tac-toe perfectly. It is possible to implement these two strategies into the program, but it is difficult. But if you think you are up for it, absolutely try it!.<br /><br /><br /> 1288789431 4133 resource View the Lab file http://inst.eecs.berkeley.edu/~cs10/fa10/lab/20/

1294864407 4134 resource Overview html

<ul> <li>Distributed computing is a field where many computers (often geographically remote) are used to solve a single problem. <ul> <li>As you can imagine, the mechanisms of this are quite complicated, and traditionally, distributed programming has been difficult (at least compared to programming on a single computer with one core).</li> <li>The scientific community cares deeply about this issue, because they often have very large computations that can only be done in a distributed way (e.g., simulating climate change). Very early distibuted computing applications were all scientific in nature.</li> <li>More recently, <em>every</em> field has large datasets and compute jobs, from entertainment (Pixar rendering a frame from their latest movie) to medicine (protein folding) to finance (running simulations of a new purchasing strategy on all historic stock exchange data) to artificial intellgence (solving checkers) to business (Google needing to crawl and index and search the web).</li> <li>Languages and tools and abstractions have improved greatly for distributed computations.</li> <li>At the end of the day, <em>Amdahl's law</em> tells us that in the perfect world, if we distribute the problem across N machines, we can solve the problem N times faster, but it's going to be hard to get that level of speedup because of serial fraction of code. Still, if N is on the order of a million and coders make every effort to reduce the serial fraction, that's a pretty fast system!</li> </ul> </li><li>There are common <em>patterns</em> that have emerged (i.e., the best ways) to approach problems with computational resources which might be geographically distant. </li><li>One of these is <em>MapReduce</em>, which has emerged as one remarkable abstraction for dealing with the difficulties of distributed computing. <ul> <li>Researchers at Google wrote the seminal paper on it, and they use it extensively to take advantage of their massive datacenters to help them with their massive data needs. In our simplifaction of the process...</li> <li>There is a <strong>Map</strong> phase where (sometimes very big) data is broken up into pieces and sent to machines with <em>mapping function</em>. Sometimes the mapping function is the identity (i.e., do nothing) function; take what is sent in and return it. The output of the mapper is the same as the input of the reducers. In our simplying abstraction, the mapping happens over a list of elements, which can be of any type (word, sentence, list, procedure, etc).</li> <li>There is a <strong>Reduce</strong> phase where all the results of the mappers are combined into one by a <em>reducing function</em>, which takes two adjacent pairs and replaces those with the reduction, and this process continues until there's only one element left.</li> <li>Note that the outputs of reductions are sent as input to other reducers, so in our simplifying abstraction, there are only two data types: <ol> <li>The data type used in the list of input to the mappers. In the tables below, the <b>Input</b> is a list of this type. (E.g., if it's a <i>number</i>, then the input to the MapReduce is a list of <i>numbers</i>.)</li> <li>The data type that is the output of the reducers, shown as <b>Output</b> below, because it's reported value of the entire MapReduce process. In this simplified model, this type is the same as the output of the mappers, which is the same as the input to the reducers. </li> </ol> </li> <li>Another way to think about it -- what if the original list were of length 1? The mapper would do its job, and return something. But, since it's the only mapper needed, its output has to match the desired output of the MapReduce call, so every mapper always has to return the same output (type, formatting, etc) as is desired (from the result of the reducing phase).</li> <li>Here's the most important part of this, so read the following over a few times so you understand: <strong>Thanks to Abstraction, running a MapReduce on your computer should be indistinguishable from running MapReduce on a cluster of a million computers (except hopefully the latter is faster). You shouldn't need to worry about that when you're writing your MapReduce code. So, for this lab, we're going to make sure you understand how to write MapReduce programs for one computer, and later when BYOB allows us to easily support automated, distributed computing, the internals of MapReduce will change to send your program to a cluster, but your programs won't have to!</strong></li> <li>How does it work? It's exactly as we describe; we send the results of mapping over a list to a reducer (block interface and definition shown below).</li> </ul> </li> </ul> <p align="center"> <img src="./CS10 Lab Distributed Computing_files/MapReduceSignature.gif" width="188" height="22" alt="MapReduce Signature"><br><br> <img src="./CS10 Lab Distributed Computing_files/MapReduceDefinition.gif" width="322" height="103" alt="MapReduce Definition"> </p> 1294865431 4135 resource Let's get started with MapReduce! html

<p>To get started, load up our finished project, <a href="http://inst.eecs.berkeley.edu/~cs10/fa10/lab/20/byob/MapReduce.ypr"><code><strong>MapReduce.ypr</strong></code></a>. Your screen should look like this:</p> <p align="center"><img src="$@FILEPHP@$$@SLASH@$MapReduceScreen.png" width="480" height="359" alt="Startup splash Screen for MapReduce BYOB project"></p> <p align="left">Now, click the green flag to get started and initialize the system. After that, you can type any number 1-5 to run one of the five MapReduces below, and '<code>r</code>' to reset to the initial state. We've given you all the answers, so you can see and understand what the problem is asking you to do and what the expected output is. </p> <p align="left">By the way, the word <em>Domain</em> means 'input', and the word <em>Range</em> means 'output'.</p> 1294866529 4136 resource Your first MapReduce : a simple sum-of-squares (we did it for you) html

<ul> <li>We're going to start by showing you how we do a really easy one, and work up to some hard ones. This problem involves finding the sum of squares of some numbers. E.g., 1<sup>2</sup> + 20<sup>2</sup> + 3<sup>2</sup> + 10<sup>2</sup> = 510 (nice area code, eh?)</li> </ul> <table width="100%" border="1"> <tbody><tr> <th scope="col">Problem</th> <th scope="col">Input</th> <th scope="col">Map Domain</th> <th scope="col">Map Range</th> <th scope="col">Map Function</th> <th scope="col">Binary reducer function</th> <th scope="col">Output</th> </tr> <tr> <td align="center">A sum of squares of numbers</td> <td align="center">numbers, each one a different list element</td> <td align="center">number</td> <td align="center">number</td> <td align="center">square</td> <td align="center">+</td> <td align="center">a single number</td> </tr> </tbody></table> <p>...and here's what it looks like when we do it: </p> <p align="center"><img src="$@FILEPHP@$$@SLASH@$SumOfSquaresMR.png" width="331" height="105" alt="Sum-of-squares MapReduce"></p> Let's note a couple things: <ul> <li>First of all, both mapper and reducer are <em>reporter</em> blocks, so we need to wrap them in grey borders so they pass in the functions themselves as data, not the results of calling multiply and addition on two empty inputs (i.e., 0). We prefer this abbreviated style, but we could also have used the <img src="$@FILEPHP@$$@SLASH@$TheBlock.gif" width="98" height="16" alt="The _ Block"> blocks and NOT used the gray borders like this (this should be review for you, btw).</li> </ul> <p align="center"><img src="$@FILEPHP@$$@SLASH@$SumOfSquaresMRtheblock.png" width="320" height="105" alt="Sum Of Squares using The Block"></p> <ul> <li>The mapper should take a single number as input, but what we've used for simplicity is just the <img src="$@FILEPHP@$$@SLASH@$Multiply.gif" width="49" height="18" alt="Multiply"> block, which has two inputs. You also recall that BYOB, given a function of two inputs but with only one input (each element in Map's input list in this case) will just copy the input to all the fields, making it a nice, effective square procedure.</li> <li>As we go through more detailed examples, we're going to want to write a <em>mapper</em> and <em>reducer</em> funtions as separate and defined blocks, so for good code management, we're going to define a sprite per MapReduce problem, each of which has a <img src="$@FILEPHP@$$@SLASH@$mapper.gif" width="69" height="18" alt="mapper"> and <img src="$@FILEPHP@$$@SLASH@$reducer.gif" width="87" height="18" alt="reducer">, with the answers already filled in. Once you understand what the problem is, first edit the <img src="$@FILEPHP@$$@SLASH@$mapper.gif" width="69" height="18" alt="mapper"> block, delete its body, and see if you can recreate it. Once you've got a working <img src="$@FILEPHP@$$@SLASH@$mapper.gif" width="69" height="18" alt="mapper">, do the same with the <img src="$@FILEPHP@$$@SLASH@$reducer.gif" width="87" height="18" alt="reducer">. That way, you'll always have a working system. Note that we've written a lot of helper functions to make your life easier. Feel free to use the <code>Scripts</code> area of each sprite for debugging. When you're done with each of these, compare your answer with ours.</li> </ul> 1294866764 4137 resource Your second MapReduce : Alpha, the first word in the dictionary html

<p>We're going to start easy and tell you how to write your mapper and reducer. In fact, this problem is so easy, it just requires you to write the reducer, since the mapper is the same as the identity <img src="$@FILEPHP@$$@SLASH@$id.gif" width="35" height="18" alt="id">! (I.e., the mapper just passes its input through, untouched, and the reducer has to do all the work!). Fill in the body for the <img src="$@FILEPHP@$$@SLASH@$mapper.gif" width="69" height="18" alt="mapper"> and <img src="$@FILEPHP@$$@SLASH@$reducer.gif" width="87" height="18" alt="reducer"> for the <code> Alpha</code> sprite and test it.</p> <table width="100%" border="1"> <tbody><tr> <th scope="col">Problem</th> <th scope="col">Input</th> <th scope="col">Map Domain</th> <th scope="col">Map Range</th> <th scope="col">Map Function</th> <th scope="col">Binary reducer function</th> <th scope="col">Output</th> </tr> <tr> <td align="center">The first word in the dictionary in all of Shakespeare's works</td> <td align="center">All of Shakespeare's works, each word a different list element</td> <td align="center">word</td> <td align="center">word</td> <td align="center">identity</td> <td align="center">Take two words and return the earlier word in the dictionary</td> <td align="center">a single word</td> </tr> </tbody></table> 1294866869 4138 resource Your third MapReduce : Love, All the Beatles song titles with the word "love" in it html

<p>Hopefully that last one wasn't too bad. This one is a little harder because you have to write both the mapper and reducer. The idea is you've got a huge set of data and you need to keep only the ones that match. Fill in the body for the <img src="$@FILEPHP@$$@SLASH@$mapper.gif" width="69" height="18" alt="mapper"> and <img src="$@FILEPHP@$$@SLASH@$reducer.gif" width="87" height="18" alt="reducer"> for the <code> Love</code> sprite and test it.</p> <table width="100%" border="1"> <tbody><tr> <th scope="col">Problem</th> <th scope="col">Input</th> <th scope="col">Map Domain</th> <th scope="col">Map Range</th> <th scope="col">Map Function</th> <th scope="col">Binary reducer function</th> <th scope="col">Output</th> </tr> <tr> <td align="center">All the Beatles song titles with the word "love" in it. This is effectively a "filter" operation, removing all the list elements that don't match.</td> <td align="center">All of the Beatles song titles, each song title a different list element</td> <td align="center">Song title (sentence)</td> <td align="center">a list of the song title; or an empty list</td> <td align="center">Look for the word "love" in the title, if it's there, return title as a one-element list, otherwise return the empty list</td> <td align="center">Merge all the lists together that the mappers (and other reducers) return into one big list</td> <td align="center">Same form as the input: a list of song titles, except each one has the word "love" in it.</td> </tr> </tbody></table> 1294866940 4139 resource Your fourth MapReduce : WordCount, a count of the number of times words appears html

<p> This one is a quite a bit harder because of all the list manipulation. The idea is you've got a huge corpus of data and you want to count all the times words appear. Fill in the body for the <img src="$@FILEPHP@$$@SLASH@$mapper.gif" width="69" height="18" alt="mapper"> and <img src="$@FILEPHP@$$@SLASH@$reducer.gif" width="87" height="18" alt="reducer"> for the <code> WordCount</code> sprite and test it.</p> <h3>A quick aside on writing lists on paper...</h3> <p>Remember the Midterm handout "Writing Scratch/BYOB code on Paper"? Well, we're going to add something to it. When you want to write a list of things, write them with an open parenthesis, then the first item, second item, etc (separated by spaces) and when you're done, put a closed parenthesis. If any of your items are a sentence, you have to put quotes around the sentence. So, for example, the list of three things:</p> <p align="center"><img src="$@FILEPHP@$$@SLASH@$rights.png" width="183" height="113" alt="rights"></p> <p>...would be written as the equivalent 3-element-list: <code>(life liberty "pursuit of happiness")</code>. Similarly, a nested list just shows up as a nested set of parenthesis. E.g.,</p> <p align="center"><img src="$@FILEPHP@$$@SLASH@$LoveHateThe.png" width="142" height="323" alt="LoveHateThe"></p> <p>...would be written as <code>((Love 5) (Hate 4) (The 10))</code>. We mention this because we've used this short-cut below. Now, on to the problem.</p> <table width="100%" border="1"> <tbody><tr> <th scope="col">Problem</th> <th scope="col">Input</th> <th scope="col">Map Domain</th> <th scope="col">Map Range</th> <th scope="col">Map Function</th> <th scope="col">Binary reducer function</th> <th scope="col">Output</th> </tr> <tr> <td align="center">For every word in Shakespeare's works, the number of times it occurs. E.g., <code>((Love 123) (Hate 4) (the 25231) etc)</code></td> <td align="center">All of Shakespeare's works, each word a different list element</td> <td align="center">word</td> <td align="center">A list of a list of two elements, the word and 1. This is the same as the format of the final mapreduce output if shakespeare would have only written one word. E.g., <code>((Love 1))</code></td> <td align="center">Make a list of a list of the input word and the number 1</td> <td align="center">Take two lists of words and their counts and merge them. E.g., <code>((Hate 4) (Love 3))</code> and <code>((Love 2) (The 10))</code> merge to <code>((Love 5) (Hate 4) (The 10))</code></td> <td align="center">a single list of lists, with each inner list a unique word and its count</td> </tr> </tbody></table> <p>Here are some tips on how to get started with <em>WordCount</em>:</p> <ol> <li>Start with the <code>mapper</code> as always.</li> <li>We've provided the <code>MakeWordCount</code>, <code>GetCount-from-WordCount</code>, and <code>GetWord-from-WordCount</code> helpers. Use them as needed.</li> <li>When writing your <code>reducer</code>, think about the general case of combining two lists as in the example above. <em>Hate</em> is only in the first list. <em>The</em> is only in the second list. <em>Love</em> is in both lists. How do you merge these two lists?</li> <li>We found it useful to write the helper <code>GetCount-of-Word-()-from-List</code> ... feel free to use this when writing <code>reducer</code>, but make sure you could write this on your own too.</li> </ol> 1294866990 4140 resource Extra for Experts : the fifth MapReduce ... Google, building a Google-like index text 1

<p> The idea here is you've got a huge set of webpages (URLs) and webpage-content and you want to create a huge table indexed by each word that shows you what URL the word is in. Fill in the body for the <img src="$@FILEPHP@$$@SLASH@$mapper.gif" width="69" height="18" alt="mapper"> and <img src="$@FILEPHP@$$@SLASH@$reducer.gif" width="87" height="18" alt="reducer"> for the <code> Google</code> sprite and test it. <em>Hint: This problem is very similar to WordCount</em>.</p> <table width="100%" border="1"> <tbody><tr> <th scope="col">Problem</th> <th scope="col">Input</th> <th scope="col">Map Domain</th> <th scope="col">Map Range</th> <th scope="col">Map Function</th> <th scope="col">Binary reducer function</th> <th scope="col">Output</th> </tr> <tr> <td align="center">Google simulation! Given web pages (URLs) and data, create a massive reverse-lookup-table, that allows us to quickly query, given any single word, what webpages it was on.</td> <td align="center">The input is a list of lists. The first element in each inner list is the web page address, the second element is the content of the webpage</td> <td align="center">Two-element list, the web page address and the text of the web page</td> <td align="center">A list of lists, where the inner list has the word as the first element and all the URLs that have the word as followup elements. E.g., if the input were: <code>("hamlet" "to be or not to be")</code>, the output would be <code>((to hamlet) (be hamlet) (or hamlet) (not hamlet))</code></td> <td align="center">For every unique word in the webpage, make a list of the word and the URL. Return a list of all these pairs.</td> <td align="center">Take two lists of words and their counts and merge them. E.g., Given<code> ((to hamlet) (be hamlet) (or hamlet) (not hamlet))</code> and <code>((to webster) (wit webster))</code>, it would return <code>((to hamlet webster) (be hamlet) (or hamlet) (not hamlet) (wit webster))</code></td> <td align="center">a single list of lists, with each inner list a unique word as the first element and the URLs that contain the word as the following elements.</td> </tr> </tbody></table> 1294867151 4141 resource Quiz Answers html

<ul> <li><em>Alpha</em> is a finding pattern</li> <li><em>Love</em> is a filtering pattern</li> </ul> 1294865896 4142 resource Internal Course Survey file https://spreadsheets.google.com/spreadsheet/viewform?formkey=dEdibm5jVlNsTW16ZFgwdldVM2VlSVE6MA

1303925988 4143 resource AP Post-Course Survey file http://www.surveymonkey.com/s/V537YSR

1303926554 4144 resource Gregory file Gregory.ypr

An AI based on ELIZA.

1279166827 4145 resource Keep score in your game of tag html

<h3>Keep score in your game of tag</h3>Now we want to keep score in our game of tag. For starters, we'll need a variable named score. Below we've shown two attempts keep score in the tag game. Do they seem like they would do the same thing (except that one says something as well)? <br /> <ul> <li>Try them both in Scratch and see if/how they work differently. </li> <li>Make sure you figure out with your partner if/how they are different. <br /></li> </ul><br /> <div style="margin-left: 40px;"><img hspace="0" height="129" border="0" width="165" vspace="0" title="There should be an image here" alt="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$tag_concurrency$@SLASH@$concurrency_no_protection.gif" /> <img hspace="0" height="149" border="0" width="180" vspace="0" title="There should be an image here" alt="There should be an image here" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$tag_concurrency$@SLASH@$concurrency_2_second_protection.gif" /><br /></div> 1278024740 4146 resource Comparing two solutions to keep score html

<h3>Comparing two solutions to keep score</h3>You might want the score to not increase when the characters are touching unless the characters are still touching after 2 seconds. In this case the script from the last step (below) should work exactly like you wanted. <br /><br /> <div style="margin-left: 40px;"><img hspace="0" height="149" border="0" width="180" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$tag_concurrency$@SLASH@$concurrency_2_second_protection.gif" alt="There should be an image here" title="There should be an image here" /><br /></div><br />However we might want it so that the score can't increase unless the characters stop touching and then touch again. In the examples below we keep track of a variable called "already touching". This variable keeps track of whether or not we've already awarded the point for the cat for catching the mouse. <br /><br />We've written two versions of the code. Your job is to work with your partner to figure out how these two versions are different. Before you try it out in Scratch, talk about your hypotheses for how they are different. <br /><br /> <div style="margin-left: 40px;"><img hspace="0" height="236" border="0" width="404" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$tag_concurrency$@SLASH@$concurrency_bad_protection.gif" alt="There should be an image here" title="There should be an image here" /> <img hspace="0" height="249" border="0" width="230" vspace="0" src="$@FILEPHP@$$@SLASH@$Images$@SLASH@$Lab02$@SLASH@$tag_concurrency$@SLASH@$concurrency_full_protection.gif" alt="There should be an image here" title="There should be an image here" /><br /></div> 1278024757 4147 resource TODO Roles of variables html

How can we use these ideas:<br />Fixed value <br />A variable initialized without any calculation and not changed thereafter.<br /><br />Stepper <br />A variable stepping through a systematic, predictable succession of values.<br /><br />Follower <br />A variable that gets its new value always from the old value of some other variable.<br /><br />Most-recent holder <br />A variable holding the latest value encountered in going through a succession of values, or simply the latest value obtained as input.<br /><br />Most-wanted holder <br />A variable holding the best or otherwise most appropriate value encountered so far.<br /><br />Gatherer <br />A variable accumulating the effect of individual values.<br /><br />Transformation <br />A variable that always gets its new value with the same calculation from values of other variables.<br /><br />One-way flag <br />A two-valued variable that cannot get its initial value once its value has been changed.<br /><br />Temporary <br />A variable holding some value for a very short time only.<br /><br />Organizer <br />An array used for rearranging its elements.<br /> 1269552041