Alex Veremeychik Mike Adams

1. Terrapin Logo"Logo is the name for a philosophy of education and a continually evolving family of programming languages that aid in its realization."- Harold AbelsonApple Logo, 1982 Alex Veremeychik Mike Adams

2. History • Terrapin Software company was founded in 1977 to market the turtle robot. • Introduced it’s first computer version on the Apple II. • Logo was originally created by Seymore Papert at MIT in 1967. • Designed on top of Lisp as a tool for learning.

3. Who is Terrapin Logo for? • Terrapin Logo was primarily designed for K-12 students. • Adaptable for all ages. • Anyone who’s interested in programming graphical patters or recursive visual algorithms.

4. Terrapin Logo Introduction • It’s most noticeable feature is the turtle, a triangular cursor used for drawing patterns. • It’s intuitive and has easily understandable commands. Such as RIGHT, LEFT, FORWARD, and BACKWARDS.

5. Introduction Continued • The top half, “Graphics”, is used for execution of programs or commands. • The bottom half, “Listener”, is used to input commands or create functions.

6. Language Features • Procedural • Responsive • Can be both interactive and not • Multi-threaded • Can draw graphics and play sounds • Limited RCX commands and features • Can implement new Logo-level RCX commands with knowledge of RCX OP-codes

7. More features • Not case sensitive • Strings are denoted by double quotes in front of the string. • Print “Hello HELLO • There are 5 basic types of data: • Words, Numbers, Lists, Property Lists, and Arrays • There are 3 types of objects: • Turtles, Bitmaps, and Controls

8. Words • Any group of characters including letters, numbers, and punctuation marks that does not contain a space and is not a primitive or procedure. • WORD? “Hello Result: TRUE • WORD? “123GO Result: TRUE • Numbers in Logo are a special class of words, that have special primitives to deal with them. • Names of all procedures in Logo, including primitive procedures, are words, although numbers cannot be used as the name of procedures.

9. Numbers • A number can be an integer, a decimal, or a number in exponential notation. • 3, 26, 4.7, 12E-7 • Valid numbers range from 1E-308 to 1E308. • All calculations in Logo have a precision of 15 digits. • Logo expresses number in the range between .000001 to 1000000 in decimal notation and anything smaller or larger in scientific notation. • Can interpret both prefix and infix notation. • + 2 2 is the same as 2 + 2 • Does correct order of operations.

10. Lists • A list is information in Logo enclosed in square brackets. • LIST? [ 1 2 3 ] Result: TRUE • Empty list is a list with no elements. Ex. [ ] • Lists within lists are allowed. • LIST? [ [RED BLUE] [ORANGE GREEN] [BLACK YELLOW] ] Result: TRUE • Some additional commands: • EQUAL?, NAME, THING, WORD, ITEM, LAST, FIRST, EMPTY?, NUMBER?, CHAR

11. Property Lists • Special type of list that allows assignment of multiple values to a single object in Logo. • Syntax: • name [property1 value1 propery2 value2 …] • Example: • DOG [BREED DOBERMAN HEIGHT [14 INCHES] COLOR [BLACK] ] • Visible Logo objects like, Turtles, Bitmaps and Controls, all have properties assigned to them, which can be edited through property lists.

12. Arrays • Special type of Logo object designed for efficient storage of structured information. • Mostly thought of as tabular forms of information with multiple rows and columns. • For example a calendar can be thought of as an array. You can write information to any particular day with three dimensions, year, month, and day. • A special type of array is the bytearray, which can be used to store numerical information where each element is a number between 0 and 255.

13. Turtles • A special type of graphics cursor. • The turtle cursor carries a pen which can draw lines through commands issued in the listener window. • The turtle can be controlled through commands such as: FORWARD, BACKWARDS, RIGHT, LEFT, PENUP, PENDOWN, and TOWARD.

14. Bitmaps • Exactly what you think it is. • An image which you can place anywhere in the Graphics window. • The main difference between Bitmaps and Turtles, is that turtles can draw and are of only a single color, reflecting their pen color. • Turtles visually reflect their heading, while bitmaps do not change visually when their heading is changed.

15. Controls • Objects for obtaining input from the users for your program. • A typical Control would be a push-button that you can click. • You determine the size and position of the Control as well as what happens when the user interacts with the Control. • Other examples of Controls are: • Check boxes, scroll bars, pop-up menus, edit fields, and list boxes.

16. Variables • Typical global and local variables. • To declare local variables use LOCAL • LOCAL “SALUTATION [HOW ARE YOU?] PRINT :SALUTATION HOW ARE YOU? • To declare global variables use MAKE or NAME • MAKE “GREETING “HELLO PRINT :GREETING HELLO • NAME “HELLO “GREETING PRINT :GREETING HELLO

17. Functions • Created using the TO keyword. TO SQUARE REPEAT 4 [ FORWARD 50 RIGHT 90 ] • To pass parameters just place them after the definition. TO SQUARE LENGTH REPEAT 4 [ FD LENGTH RT 90 ]

18. Conditionals • IF • IF expression [then-instructions] IF expression [then-instructions] [else-instructions] IF expression THEN instructions IF expression THEN instructions ELSE instructions • TEST (has to be issued before IFTRUE and IFFALSE) • TEST statement • IFTRUE • IFTRUE instructionlist • IFFALSE • IFFALSE instructionlist

19. Loops • REPEAT, FOR, EACH, FOREACH, WHILE • REPEAT number list • REPEAT 5 PRINT [HELLO WORLD] ] • FOR word number number runlist • FOR "I 1 4 [PRINT :I] • EACH list • EACH [SETH WHO * 360 / 16] • EACH is controlled by WHO, and typically used for turtles • FOREACH list runlist • FOREACH [JOHN MARTHA] [print "?] • WHILE testlist runlist • MAKE "X 1 WHILE [:X < 5] [PRINT :X MAKE "X :X + 1]

20. Multiple Turtles • 16 possible turtles can be used at the same time CS TELLALL 0 15 SHOWTURTLE EACH [SETH WHO * 360 / 16] ;set direction EACH [FORWARD 8 * WHO] ;move based on id

21. More Turtles • Turtles follow each other. TO SETUP CS SETTURTLES 4 TELL 0 PU SETXY [ 100 100 ] ;pen up TELL 1 PU SETXY [ -100 100 ] TELL 2 PU SETXY [ -100 -100 ] TELL 3 PU SETXY [ 100 -100 ] TELL ALLTURTLES ST PD ;set pen down TO CHASE ASK 0 [SETH TOWARDS ASK 1 [GETXY] FD 1] ;FOLLOW 1 ASK 1 [SETH TOWARDS ASK 2 [GETXY] FD 1] ;FOLLOW 2 ASK 2 [SETH TOWARDS ASK 3 [GETXY] FD 1] ;FOLLOW 3 ASK 3 [SETH TOWARDS ASK 0 [GETXY] FD 1] ;FOLLOW 0 CHASE

22. RCX Commands • To start communication with RCX • RCX.OPEN port RCX.OPEN “USB • Motor control • MOTOR number-or-list power MOTOR number-or-list power duration MOTOR number-or-list power “FALSE • Stop RCX execution • RCX.HALT • Close communication • RCX.CLOSE

23. RCX Sensors • Set sensor type • SETSENSOR number type SETSENSOR number type datatype SETSENSOR number type datatype slope • Type can be SWITCH, TEMP, LIGHT, ANGLE • :SENSORn is a built in variable for the sensor ports where n is 1-3. • To read a sensor simply type .SENSORn and the value will be displayed in the Listener window.

24. RCX Limitations • Logo does not provide full built-in support for the RCX. • If you are familiar with the RCX byte codes you can directly program the RCX with .RCX list. • .RCX list sends direct byte codes to the RCX brick.

25. Blind Movement • RCX.OPEN "USB TO RUN.UNTIL.HIT SETSENSOR 1 "SWITCH ;set touch sensor MOTOR 3 65 ;move forward at 65 speed WHILE [.SENSOR1 = 0] [] ;while we don’t hit anything MOTOR 3 -50 ;when hit, reverse 50 MOTOR 1 -25 ;turn slightly WAIT 100 ;keep backing up MOTOR 1 25 ;realign the wheels WAIT 5 MOTOR 1 0 ;turn off turning motor RUN.UNTIL.HIT ;recursively call self

26. References • Terrapin Logo homepage: • http://www.terrapinlogo.com • Logo Foundation website: • http://el.media.mit.edu/logo-foundation/logo/index.html • Terrapin Reference Manual • Terrapin Tutorial