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Super Logo (Tandy) - TRS

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1. QOXXXXXXXXXXXXXX SOXXXXXXXXXXXXXX QOXXXXX XXXXX PENCOLOR expr PC PENDOWN PD PENERASE PENUP PU allows selection of the turtle pattern to be used The pattern is made up of 16 rows of 16 X or characters When the turtle shape is set in this way the turtle does not visibly rotate on the screen to reflect its current heading but always displays the same orientation The X and characters may be arranged as 16 lines of 16 or any other way that adds up to 256 bits Inter vening spaces are ignored sets the pen color of the current turtle to color 0 1 20r 3 The default color is 0 The actual color depends on the current color set If the pen color is set to the same color as the screen back ground color then the turtle pen will erase as it moves tells the current turtle to draw a line as it moves in response to FORWARD or BACK commands sets the current pen color to color 3 background tells the current turtle not to draw a line as it moves in response to FORWARD or BACK commands 173 PRINTSCREEN expr RIGHT expr SETHEADING expr SETPEN state color 174 PS RT SETH and SH causes a printer screen dump to a dot matrix or color printer The screen dump produces a paper copy of exactly what is shown on the display screen The expression value should be set depend ing on the type of printer in use 1 RS DMP 110 sin
2. 7 exactly to the turtle shape commands D R L F Only is missing and while B is very useful it is not essential Use of DOODLE mode continually shows you the current heading which is help However the turtle drawn in DOODLE mode will not look exactly like the final turtle for several reasons Lines drawn in DOODLE mode are two dots wide but lines drawn as turtle shapes are one dot wide Also lines which cross comple ment when they are turtle shapes Lines which cross in DOODLE mode do not complement However you will get to see the shape in about the final form and of exactly the final size while drawing it Once you have the shape completed in DOODLE mode you can enter EDIT mode and convert the procedure into one to draw the new shape Simply insert the SHAPE command before the command list and convert each 3 to U each 4 to D each 5 to R each 6 to L and each 7 to F all by overtyping Of course you will be converting the corresponding DOODLE mode symbols not the numbers 3 7 Let s begin with a very simple example We want the turtle to appear as an arrow On graph paper we draw the dot pattern z X 88 actual turtle position is to be at the tail end of the arrows Get into DOODLE mode name the procedure NEW and draw the figure The keystrokes are 777777766677555537755747 You may be surprised at the small size of the turtle but you can always dra
3. 57 13 DOODLING idea DOODLE mode extended to open ended set of single keystroke tions if we give up the ability to store and edit the child s input as a procedure This requires a set of procedures which we hereafter refer to as the OK Set One Key Set To start we define a set of procedures with single character names To call forth the desired action the child presses the single key and then presses ENTER This is easier shown than described The first step is to define a set of procedures which match the individual keys in DOODLE mode Because we are not going to save or edit the procedures we do not bother to draw the special symbols at the bottom of the screen although if there was some reason to have them we could draw them with turtle commands Clear the memory and enter the following procedures TO 1 TO 2 CLEAR HOME END END TO 3 TO 4 PU PD END END TO 5 TO 6 RT 45 LT 45 END END TO 7 TO 8 FD 1 FD 16 END END TO 9 TO RT 15 LT 15 END END This set of procedures will allow the child to move the turtle freely around the screen in RUN mode using the keys he or she already knows from DOODLE mode The advantages of this approach become evident when we add to the list of procedures The following procedures are typical TO T TO TRI SIDE SH HT PD FD 8 IF SIDE lt 2 STOP RT 150 FD 15 REPEAT 3 RT 120 FD SIDE TRI 15 TRI SIDE 2 SH 305 FD 8 SH PU
4. 80 179 31 100 102 44 172 177 169 45 169 129 175 59 59 177 86 112 123 169 55 16 103 179 103 43 95 173 86 33 173 37 173 33 173 37 173 173 37 173 147 43 123 124 125 43 11 45 113 164 60 101 109 169 43 162 43 44 44 175 19 179 43 175 37 173 queue quote mark QUOTIENT RANDOM random sentences random words READCHAR READLIST RECTANGLE recursion RC relational operators REMOVE REPEAT REQUEST RESET RESULT return results RIGHT RL ROUND RQ RT RUN Mode save save partial scale scan screen coordinates screen dimensions screen dump scroll scrunch SE search search string SEND SEND 255 SEND words SENTENCE SETH SETHEADING SETPEN SETX SETY SH SHAPE SHIFT up arrow in EDIT Mode SHOWTURTLE SHUFFLE shutter speed SIN single key commands in DOODLE mode in EDIT Mode single space single step SLOW sorting spaces split line split screen 101 176 179 85 179 127 123 117 179 120 179 19 45 117 179 177 150 11 170 120 179 6 112 179 111 8 175 120 179 180 120 179 8 175 15 19 166 41 162 42 11 17 165 165 43 17 25 75 164 11 110 180 75 164 75 99 170 101 137 110 180 37 175 37 175 175 37 175 37 175 37 175 87 175 181 75 10 175 135 43 102 180 55 167 164 43 49 78 170 130 101 163 7 25 165 square bra
5. TO A TO D END Note that we skipped B and C because they are actually used Note also that it is not neces sary to have individual END statements for each procedure because the following TO state ment automatically ends each procedure These procedures prevent the message I DONT KNOW HOW TO if the child accidentally enters an unlabeled key In this chapter we have introduced the idea of building shapes or complex picture elements which the young child can call forth with single keystrokes The examples we have given are simple but the only limit to what is possible is your time and imagination Let s now start thinking about ways to use these tools with very young children 62 14 USE OF DOODLE MODE AND SET In the last two chapters we covered the operations of the DOODLE mode the Set What is possible and what is worthwhile are two separate questions this chapter we will pass along some suggestions for worthwhile activities Our suggestions are aimed at the adult who is working with small children We have collected ideas from a number of sources How ever we should make it clear that because Super LOGO offers possibilities for working with much younger children than could be reached previously no one at this time really knows what is possible or what is most beneficial Also remember that this is a user s manual for a computer language not a textbook on early childhood education Don t be hesitant to
6. zero Also make sure TO is in column 1 Check also that the name is correctly spelled If the name was not supposed to be a procedure then probably there 1s something wrong with the immediately preceding command 182 I CAN T FIGURE OUT I DONT KNOW HOW MUCH gt OR NOT RIGHT I DO THAT IN THIS MODE MY MEMORY 15 TOO FULL OUT OF BOUNDS I EXPECTED A HERE IMPROPER LIST 9 is filled in with the word that caused the confu sion Super LOGO was attempting to compute the value of an expression when it encountered the prob lem Possibly the syntax of the expression is in error or a colon is left out before a variable name or a function name is misspelled This message means that a command such as RIGHT or FORWARD which should be followed by a number is not followed by a number Either an expression is not present where one should be or the very first item in the expression is not valid A left parenthesis is not found as expected after an IF WHILE or REPEAT expression or after an ELSE Or unbalanced parentheses are detected A command other than one of the ones allowed for example WHILE is entered directly from the key board in RUN mode Remember some commands may be executed only within a Super LOGO procedure The internal program and work area is filled This will always happen eventually if a program is allowed to do infinite recursion call itself repeatedly forever
7. A number of other projects are possible but they quickly become so complex as to limit their value For example a procedure to turn a noun into its plural form might be useful However there are so many exceptions to the rules that its utility is limited Instead of continuing to generate sentences we will turn to examples where the words on lists are unrelated or where the relations between the words are simpler than the relations between English words in sentences Note Before continuing or shutting off the computer you may want to save the proce dures in Chapter 22 to disk A later chapter will use some of these procedures 127 28 GENERATING SORTING LISTS In this chapter we give examples of manipulation of lists of numbers and words The relation ships between the words in these lists will be simpler than the relationships between words in English sentences It is ironic that some of the best examples of list processing are mathematical for list process ing was designed to handle sentences series is a list of numbers later members of the serles are derived from the earlier members by straightforward mathematical operations One Interesting example is the Fibonacci series It is easy to generate because each new member of the series is the sum of the previous two members And it is an accurate representation of a surprising number of systems found in nature The interested reader should look at Discouer ing Apple LOGO
8. ELSE PRINT NOT CORRECT END 2 3 6 NOT CORRECT This works but we can do better It would be nice to use the RANDOM function to make the computer make up questions and it would be nice to present the question as it might appear in a book 118 with the answer in line We ll make the presentation of the problem the job of the subproce dure PICK Then our main procedure is TO DRILL ANSWER GUESS FT REPEAT 5 PICK MAKE ANSWER RESULT MAKE GUESS RC PRINT SE CHAR 32 GUESS IF GUESS ANSWER PRINT GOOD ELSE PRINT NOT RIGHT END We ve decided to give 5 problems PICK must pick the two addends print them on the screen and output the sum back as the result which is assigned to the variable ANSWER TO PICK A1 A2 MAKE 1 RANDOM 5 MAKE 2 RANDOM 6 PRINT CHAR 32 CHAR 48 1 PRINT LPUT CHAR 48 A2 OUTPUT A1 A2 END The first two lines are familar from earlier work with turtle graphics the PRINT lines con tain new ideas We want to print the value in 1 but not in the first column because of a sign with 2 Therefore we want to make a list with a space as the first word and the digit in A1 as the second word We can t just enter a space from the keyboard because a space means the end of whatever precedes it so we use the CHAR function to generate a space character within the list CHAR 32 gives a space Lists are lists of words and the value in A1 is a number
9. N in the main procedure refers to a different memory location than the variable N in the subprocedure If we want a variable to be local to a procedure we mention it in the TO statement which begins the procedure We also can create global variables variables which use a common mem ory location in all procedures in which they appear Global variables are created when you use them in a procedure without including them in the TO statement This provides one way to share information among procedures 30 DESIGN contains our first example of arithmetic expressions here 360 For a while we ll use only the standard four arithmetic operations addition subtraction multiplication and division f No parentheses are needed unless the order of operations is non standard Thus in Super LOGO 2 3 4 10 2 3 4 14 The following procedures give additional examples of the use of variables and arithmetic expressions TO SQUIGGLE FD 7 REPEAT 8 FD 4 RT 45 FD 7 REPEAT 8 FD 4 LT 45 FD 7 END TO SQUIGGLE8 SIDE ANGLE REPEAT 360 REPEAT SIDE SQUIGGLE RT ANGLE REPEAT 366 ANGLE REPEAT SIDE SQUIGGLE LT ANGLE END Notice the use of the nested REPEAT twice in SQUIGGLES If ANGLE were 180 and SIDE were 4 then each of the pairs of nested REPEATs will repeat 2x4 or 8 times Try SQUIGGLE8 1 26 SQUIGGLE8 60 SQUIGGLE8 4 90 31 8 COLORS Turtle tracks be col
10. There are many ways one can sort a list This is a topic of continuing interest in computer science and you might want to write Super LOGO procedures which implement the various strategies Here we ll sort by making a new list We ll take each item on the old list and insert it where it belongs in the partially completed new list We need a procedure which inserts a word into a list at a given position 130 INSERT LIST WORD P J MAKE J REPEAT P 1 MAKE J SE J FIRST LIST MAKE LIST BF LIST OUTPUT SE SE J WORD LIST END INSERT begins with an empty list Words are transferred to list J one at a time until the position for the new word is reached The variable P is the position Then two SE functions are used to put together the copied list the word to insert and the rest of the list This proce dure should be tested try FT INSERT AA CC EE GG B 2 PRINT RESULT AA B CC EE GG Next we ll write the main procedure First we transfer the first word to a new list Then we take words from the old list and decide where to put them in the new list TO ALPHA LIST NEW W P FT MAKE NEW SE FIRST LIST MAKE LIST BF LIST WHILE LIST lt gt MAKE W FIRST LIST COMPARE W NEW INSERT NEW W RESULT MAKE NEW RESULT MAKE LIST BF LIST PRINT NEW END We use the subprocedure COMPARE as yet unwritten to compare the word in W with the words in the list NEW and to output the positio
11. 109 178 178 169 43 41 41 101 119 129 178 12 38 27 171 7 172 19 172 172 29 176 33 44 33 172 147 42 166 55 130 132 INDEX complement concatenation condition control statements convert number to word COS count words cursive cursor cursor position CT DECK delete character delete to end of line delete line DIAMOND dice games DIFFERENCE DOODLE mode DOODLE mode used to design turtle shapes DOT double space DRAW DSKINI dynaturtles ECHO edit DOODLE Mode EDIT Mode editor summary ELSE empty word end loop recursion END erase DOODLE Mode error messages exchange letters EXP exposure expression fast search FD FENCE Fibonacci series film find find again FIRST format FORWARD FPUT fractal FRACTAL FS FT full screen 91 101 119 177 80 11 79 168 129 102 178 124 72 15 16 172 135 16 163 75 164 41 75 164 184 24 149 149 179 55 167 89 38 172 43 25 165 172 41 162 102 44 172 56 15 163 17 83 168 109 45 19 47 168 56 182 145 113 43 31 175 75 6 172 168 129 43 75 164 75 164 108 178 184 6 172 110 178 50 51 25 172 172 25 FULLSCREEN FULLTEXT functions game controller games games dice general message global find global variable HATCH heading HEADING HIDETURTLE Hilbert curve Hofstader home HOME horizontal size HT hyphen
12. 13 18 24 32 24 O 2 3 END R45 R90 R135 R135 R45 R45 R90 R45 R45 L45 L45 R45 L45 LINES 1 4 1 4 1 4 5 6 7 9 5 6 1 4 5 6 7 9 7 9 5 6 1 4 49 First look at the diagram The program tries to reach the lowest level of the procedure until forced to rise in level by the STOP or the END statement We can single step the program by running it as follows In RUN mode type TRACE TREE 32 Now every time you press one command in the procedure will be executed For example when you start the first displays the call TREE 32 at the bottom of the screen The second executes the call and displays the next line IF N lt 18 STOP at the bottom of the screen The third checks the condition N lt 18 and finds it false remember we start with N equal to 32 Therefore the remainder of the line is to be skipped the STOP so the next line FD N is displayed The fourth executes FD N which you can see and displays RT 45 the fifth executes RT 45 again visible and the sixth executes the recursive call TREE 3 4 You can follow the table exactly as long as you realize that the statement IF N lt 18 STOP is one statement if the condition is false but two statements if the condition is true execute the STOP A step in the table is counted as all the lines executed from when a level is entered until the level is exited A level can be exited in three ways by a STOP or an EN
13. ANSWER T PRINT WRONG END 117 QUES3 PRINT COWS CAN FLY PRINT TYPE T FOR TRUE PRINT TYPE F FOR FALSE TEST RC F IFTRUE PRINT SE F RIGHT IFFALSE PRINT SE T WRONG END In the first and third examples we have combined the letter and the feedback into a sentence In the second example we have transferred the letter into the variable named ANSWER so that we can do several things with it print it and use it in two conditions The third example also illustrates a useful alternative to the IF THEN ELSE control statements The TEST statement tests whether the expression is true or false and saves that information for future reference The list of commands following the IF TRUE will be executed only if the result of the TEST statement is true The list of commands following the IFFALSE statement will be executed only if the result of the TEST statement is false The TEST IFTRUE IFFALSE combination is most useful when the test and the actions which are to depend on that test are somewhat separated within a procedure Next we move to an arithmetic drill The procedures will turn out to be a bit more complex than you might expect but they form a good illustration of some important differences between numbers and words To keep things simple we want to present some single digit addi tion questions Try TO ADD SUM FT PRINT 2 3 MAKE SUM RC PRINT SUM IF SUM 5 PRINT CORRECT
14. First Edition Super LOGO program 1984 Micropi All Rights Reserved Licensed to Tandy Corporation Super LOGO manual 1984 Micropi All Rights Reserved Licensed to Tandy Corporation Reproductionor use without express written permission from Micropi and Tandy Corporation of any portion of this man ual is prohibited While reasonable efforts have been taken in the preparation of this manual to assure its accuracy and Corporation assume no liability resulting from any errors or omissions in this manual or from the use of the infor mation obtained herein Please refer to the Software License in the front of this manual for limitations on the use and reproduction of this Software package FOREWORD For more than a decade the authors have been involved in the use of computers in education and particularly with Computer Assisted Instruction Our experience made us aware of prob lems in getting students started on the right track in programming and of LOGO s potential to help solve those problems We decided that it would be worthwhile to develop a version of LOGO which ran on low cost hardware and allowed relatively long sets of procedures Color LOGO met those objectives and allowed the addition of some features notably multiple turtles Now more memory is available at low cost and we have the benefit of feedback from many users Super LOGO makes use of both those developments larger ROM packs mad
15. HOME LEFT expr LT NOECHO 172 paints the entire display area the background color and moves the current turtle to the home position Erases the text window selects color set 0 or 1 For each set there are four distinct colors The default colorset is Draws a one pixel dot of the current pen color at the current turtle location Erases the text window and places the screen in FULLSCREEN mode turns on ECHO mode When echo mode is on then all characters displayed on the screen via TEXT PRINT or REQUEST commands are also printed on the printer If the printer is not ready then data is displayed only not printed moves the turtle forward the number of steps denoted by the value of the expression If the tur tle s pen is down then a line of the current pen color is drawn as the turtle moves places the screen in FULLSCREEN mode This allows the turtle and lines to be visible on the entire screen places the screen in FULLTEXT mode This dis allows the drawing of any turtle graphics and uses the entire screen as a text viewport makes the turtle invisible sends the current turtle to position 128 96 with heading turns the turtle left counter clockwise the speci fied number of degrees turns off ECHO mode uo 009 0 cR o cr is XAXXXXXXX 954 20s uos 2 CU Sp
16. It must be converted into a word before it can be used in a list Again we use the CHAR function The digit 0 is CHAR 48 and the remaining digits follow in order so CHAR 48 1 gives one digit word The concatenation operator ff combines the two words space and digit into a list The next PRINT command uses the same technique to con vert the value into a word but it uses a different function to combine the two words and digit into a list The LPUT function expects a word and then a list and it adds the word to the end of the list Now we return to examination of the main procedure The response from the keyboard is assigned to the variable GUESS Printing the value in GUESS will print it in the first column of the screen This time we indent by making a list from a space CHAR 32 again and the value in GUESS with the SE function The combination here is simpler than in PICK because the value in GUESS is a word the RC function always returns a word The rest of the procedure is straightforward 119 As we shall see the next procedure we can use the READLIST abbreviated RL function when we want more than a single character from the keyboard As the name of the function indicates the result of this operation is a list even if the list is only a single word long The input from the keyboard is treated as a list which is ended when the user presses the key There is no formal limit to the length of the list other than
17. N Y HATCH T 1 FIR2 N X Y IF N gt 20 STOP FIR N 1 X Y T END EVERGREEN 5 DRAW WHILE TREES gt 0 MAKE X RANDOM 200 20 MAKE Y RANDOM 100 30 MAKE TREES 3 HATCH FIR 2 X Y T REPEAT 30 MAKE TREES 5 1 VANISH END EVERGREEN S 84 Try running this set of procedures first with one tree EVERGREEN 1 and then with several EVERGREEN 4 EVERGREEN 5 With some TV sets you may be able to get green tops and brown trunks so try playing with the color adjustment knobs If not you can always claim that they re intended to be blue spruce There are a couple of new ideas in the last two procedures In FIR11 we have used the XLOC function This returns the x screen coor dinate of the designated turtle Here X is the starting point for the right half of the tree When XLOC has returned to the starting point the procedure is finished In FIR notice the use of the variable to indicate the turtle number In EVERGREEN we have introduced the RANDOM function RANDOM produces a random integer between 0 and the argument 1 For example RANDOM 266 26 adds 20 to a random number between 0 and 199 The result must be a number between 20 and 219 We do this to keep the trees away from the edge where the wrap around will give some rather lopsided trees Also note the use of WHILE in combination with the MAKE TREES TREES 1 This gives a number which is one less e
18. Once the rate is set it remains unchanged until reset by another BAUD command or until the computer is turned off When the computer is turned on the baud rate is automatically set to 600 Next from BREAK mode enter P for single space or Q for double space and the contents of memory will be printed If for some reason you want to eliminate the line feed at the end of any line thus using a larger portion of the paper width enter EDIT mode and insert an character at the end of every line for which you want to eliminate the car riage return and line feed To place character in a line in EDIT mode you ll need to press the key twice There remains the question of saving results the pictures and or text on the screen One way 15 to take pictures this 16 the only way to get color if you don t a Radio Shack Color Printer To avoid false patterns due to interactions of the camera shutter with the video display we recommend a shutter speed of second Use a tripod and a cable release for the camera The lens setting is somewhat dependent on the brightness setting of the TV and of course on the film speed good starting point is to set medium brightness on the TV and use a lens opening of about f8 with film speed of 100 ASA The reds are likely to come out rather brownish and commercial developers are likely to overexpose prints with large dark back grounds However the illustrations in this manual are typical of wh
19. The character is not echoed to the screen when it is typed synonym for REQUEST accepts a sentence or list of words separated by spaces from the terminal and returns the result as a list The words may be up to 13 characters each The left arrow key may be used to backup and correct errors only within individual words The ENTER key is used to end the list returns the value last saved by the OUTPUT statement It will be the value returned by a called procedure 179 ROUND arg SENTENCE ab SE ab SIN arg SUM xy THING word WORD ab XCOR YCOR XLOC arg YLOC arg 180 returns the nearest integer to the arg value a and 6 represent words or lists This function returns a list consisting of all elements of the input lists returns the sine of arg degrees returns x T y returns the value associated with the word b must be words This outputs a word consisting of the characters in a followed by the characters in b returns the X coordinate of the current turtle returns the Y coordinate of the current turtle returns the X coordinate of the turtle with the specified identification note XLOC ME gives your own X coordinate If no turtle exists with the identification then 128 is returned returns the Y coordinate of the turtle with the specified identification note YLOC ME gives your own Y coordinate If no turtle exists with the identification then 92 is returned TURTLE SHAPE LIST The SHAPE
20. connect dots with two keystrokes key producing FD 10 each stroke We have to adjust PATTERN1 as well PATTERN1 DOTS SX 5 SY 150 REPEAT 6 PD FD 20 PU FD 20 SX 5 SY 50 ST PD END You may be wondering why we didn t just give you the final versions immediately The point is that we hope you will try creating your own exercises and we want you to see that a little attention to detail can make the exercises much more effective Be sure to try out the task to check the difficulty level before the children are around This is supposed to be fun as well as Instructive not a new source of frustration The same pieces can be used for a slightly more difficult exercise PATTERN2 DOTS SX 5 SY 156 REPEAT 6 PD 60 FD 40 RT 120 FD 40 LT 60 SX 5 SY 55 96 FD 10 RT 90 FD 40 RT 90 FD 10 10 LT 90 5 END 65 Here the task is to reproduce the pattern by continuing the shapes started the lower line Because the two shapes forming the pattern are different the focus is on the shape rather than straight copying We may as well make use of some of the fancier shapes that we have defined in the OK Set The following is another example of complete the pattern but one which is visually more interesting In order to run the following procedure you ll need to have the final versions of the procedures T T1 and TRI from Chapter 13 in program memory TO PATTERN3 MAKE X 0 MAKE Y 50 CLEAR HT REPEAT 10 REPEA
21. of TREE lines 4 and 6 of the procedure somewhat different thus producing an asymmetrical tree You also could try changing the angles but notice that the sum of the two right turns is equal to the left turn Now let s try to understand the program We have introduced two new ideas in line 1 The first is the conditional The must be followed by an expression which has a truth value In TREE the expression is N lt 2 If the current value of N is less than 2 then this expression is true and the rest of the state ment will be executed If the current value of is 2 or greater then this expression is false and the rest of the statement will be skipped The rest of the statement is placed in paren theses it may consist of many commands and it may extend over many lines The second new item in line 1 is the control statement STOP The STOP statement ends a procedure STOP has the same effect as an END statement but an END statement can appear only at the end of a procedure It will be easier to understand TREE if we make some changes to simplify it Change the condition in line 1 to N lt 18 and change the right turns lines 3 and 7 to 45 and the left turn line 5 to 90 Then run TREE 32 to get a simpler tree 48 The following diagram and table outline the operation of TREE g O B Br D TA FeO oo hr ct e Level Level Level Level 32 24 18 13 18 13 18 24 18 13 18
22. thus there may be any number of local variables in a procedure If a variable is referenced in a procedure but is not on the TO statement for the procedure then the variable is said to be a global variable There is only one storage location assigned to each particular global variable Thus all references to the global variable refer to the same storage location even if the references are in different procedures This provides a way of shar ing information among procedures or among turtles LISTS A list is a value consisting of any number of words stored in some given order A list with no entries is called a null list Super LOGO restricts the entries in a list to being words not other lists Examples of valid lists are ABLE BAKER CHARLIE DOG THIS IS A LIST ARITHMETIC OPERATORS These operators result in a number from 32768 to 32767 plus up to two places after the deci mal point Division uses only the integer part of the arguments and produces a result of limited accuracy The other arithmetic operators act on the integer and fraction and produce more accurate results addition subtraction multiplication division 176 LOGICAL AND RELATIONAL OPERATORS These operators always result in TRUE or FALSE Within an expression context a numeric 0 is considered FALSE and all other numbers are considered TRUE amp logical AND logical OR NOT logical negation RELATIONAL OPERATORS lt less than gt greater
23. IF IFFALSE IFTRUE indentation INSERT insert character insert line INT interrupt KEY keys DOODLE mode LAST LEFT LENGTH length list lens opening level line feed LIST lists list length literal load local variable logical operators LPUT LT MAIL MAIL 255 mailbox MAKE marker master procedure master turtle J K L 25 165 172 108 166 172 112 177 102 97 149 99 164 30 176 77 168 37 102 178 9 172 53 45 37 69 165 38 172 11 10 172 27 88 50 168 118 169 118 169 21 131 16 164 17 163 129 178 86 98 178 55 108 178 9 172 124 120 43 25 47 43 162 178 107 176 120 98 177 41 162 30 176 177 110 119 178 9 100 179 101 99 67 114 169 42 163 25 77 ME MEMBER memory full METAMORPHIZE merge message mode mode map multiple turtles multiprogramming multitasking NEAR nesting Newton s Law NOECHO NOT NOTRACE NOWRAP number to word numbers range OK Set One Key Set OR order of operations OUTPUT overlay overtype PADDLE paddle sensitivity partial save PAT pause PC PD PENCOLOR PENDOWN PENERASE PENUP permutations of letters pictures PICK PICKRANDOM pig latin photographs polygons POLYSPI power primitives PRINT printer printers printing text PRINTSCREEN procedure names PRODUCT PS PU 82 125 45 126 42 162 99 15 161 15 77 181 77 77 181
24. In general procedure calls hatching turtles and sending messages consume memory The longer the text in the program area the less available memory for these operations The screen has been placed in NOWRAP mode and a turtle has run off the boundaries of the screen 42 is WORD LIST or NUMBER and this indicates that the improper type of data was given to a func tion For example SENTENCE expects words or lists for arguments not numbers A list within the program does not end before the end of the line or it contains a P 183 atendof line as literal character ABS adding procedures address alphabetize all points bulletin AND animation append ARC argument arithmetic arithmetic drill arithmetic operators arrow keys ASCII assignment BACK backspace BACKGROUND BAUD baud rate baud default BF BG BK BL blackjack bottom up break line BREAK Mode BUTFIRST BUTLAST BUTTON call camera settings cassette cassette volume CHAR circle CIRCLE CLEAN clear clear memory CLEARSCREEN CLEARTEXT colon color color printer COLORSET combinations of letters combining procedures commands RUN Mode commands single key COMPARE compare word 43 43 112 177 42 99 131 99 177 87 91 42 162 38 111 31 118 176 163 98 101 129 177 67 9 171 56 33 171 42 171 42 42 108 177 33 171 9 171 108 178 140 26 17 6 161 108 109 177 108
25. MAN2 DELAY 800 SX XLOC ME DELAY 500 SX XLOC ME DELAY 500 SX XLOC ME DELAY 500 SX XLOC ME REPEAT 3 HT DELAY 20 ST DELAY 30 END loo TO TUNNEL 1 HT SX 60 SH 0 REPEAT 18 FD 20 RT 124 FD 56 BK 56 LT 104 END 1 SHAPE RRUFFFLLDFLFR FFLFFRRRFLLFFRRF LFLLLFFRRFLFRRFL FFLFLFLFLFFLFRFF FFLLFRRRFLFFRFL FFRRFF END 153 2 SHAPE RRUFFFLLDFF FFLFFRRRFLLFFRRF LFLLLFFRRFLFRRFL FFLFLFLFLFFLFRFF FFLLFRRRFLFFFFFF END TO PAINT PC 2 HT MAKE 1 REPEAT 3 COLORSET 0 DELAY 100 COLORSET 1 DELAY 100 SX 114 SY 102 SH 0 REPEAT 13 RAGGED X SX XLOC ME 6 SY YLOC ME 2 MAKE X X 5 END TO RAGGED REPEAT 8 FD X RT 135 FD 8 BK 8 LT 90 END TO DELAY TIME REPEAT TIME END 154 next set 16 for younger audience TO CLOCK DELAY INT CLEAR DRAW CLOCKFACE TIME DELAY INT END TO CLOCKFACE MAKE NUMBER 12 SY 180 SX 104 SH 90 REPEAT 12 FD 22 RT 902 FD 5 BK 5 PU 10 PRINT NUMBER FD 10 LT 90 FD 22 RT 30 MAKE NUMBER NUMBER 1 IF NUMBER gt 12 MAKE NUMBER 1 END TO TIME DELAY INTERVAL HT REPEAT 24 MAKE HR 0 WHILE HR lt 12 MAKE MIN 0 WHILE MIN lt 60 DIGITAL HR MIN PC 1 LITTLEHAND HR MIN PC 2 BIGHAND MIN REPEAT DELAY PC 3 LITTLEHAND HR MIN BIGHAND MIN MAKE MIN INTERVAL MAKE HR HR 1 END TO BIGHAND MINUTE SX 128 SY 96 SH 6 MINUTE LT 8 FD
26. ST END END 59 T will draw triangle You might wonder why is so elaborate after all we could use the fol lowing to draw a triangle TO QUICKT REPEAT 3 FD 15 RT 120 END The problem here is that the orientation of a triangle drawn by QUICKT will depend on the prior heading of the turtle For the applications we have in mind we want all the triangles to have one vertex pointing up SH 0 We also want to color in the triangle and we want to draw the triangle around the turtle s starting position Therefore we use the procedure TRI and we move forward eight units before starting the triangle hiding the turtle gains speed TRI uses recursion to make a filled in triangle To get complete filling in we must start at the correct vertex of the triangle this is not obvious but is a consequence of the way in which the Color Computer produces color in high resolution Thus the line RT 150 FD 15 in moves us to a different vertex You might try replacing this line with RT 36 to get a striped triangle and then make TRI read REPEAT 4 RT 129 FD SIDE to get an even more interesting pattern The commands after TRI 15 return the turtle to the starting position with a heading of 0 degrees A similar set of procedures can be used to define a box and a circle TO B SH 45 PD FD 10 RT 45 BOX 14 RT 135 FD 16 SH PU ST END TO BOX SIDE IF SIDE lt 2 STOP REPEAT 4 RT 90 FD SIDE BOX SIDE 1 END TO C SH
27. a new pattern of 16 x 16 dots The PAT must be followed by the pattern For example the sequence m the following procedure will change the turtle shape into a small person shape 95 SPACEPERSON AXXXXXXXXXXXXX AXXXXXXXXXXXXX RT 90 SETX 1 REPEAT 20 FD 5 WAIT 3 END The dots indicate the positions where nothing should be drawn that is they remain the back ground color and the X s indicate positions where the turtle foreground color should be drawn Here we have given the pattern in 16 rows of 16 dots That is the easiest to see but the 16 x 16 256 dots can be given in any desired arrangement for example 8 x 32 256 While the PAT command makes it easier to give a sizable turtle which is filled in it is limited in one sense The turtle defined by a PAT command does not rotate on the screen That is the turtle appears to face the same way whatever the current turtle heading This means that the PAT should be used in situations where the turtle does not rotate for example two PAT com mands could be used in place of the SHAPE commands in ONE and TWO above for WALK but not for WALK AROUND or in situations where rotation is not visible for example using a turtle as a sun which moves across a scene It
28. a place in which an expression can be substituted An expression can be a number a variable a function reference a word a list or a combination of these and the operators shown below Expressions may contain parentheses to denote the grouping of operations or sub expressions NUMBERS A number may have a value from 32768 to 32767 plus up to 2 decimal places decimal point must be preceded by at least one digit Examples of valid numbers are 12 0 53 12345 67 99 99 WORDS A word consists of a quote character followed by from 1 to 13 letters or digits Examples of valid words are HAPPY ABC123DEF456 175 VARIABLES A variable is a word which has a value associated with it The value may be a word a number or a list To refer to the variable name use the notation TOTAL That is a quote followed by the name To refer to the value associated with a variable use the notation TOTAL or THING TOTAL That is a colon followed by the name or the word THING followed by the name If a variable is given on a TO statement then that variable is said to be a local variable That is each time the procedure is invoked a new storage location is assigned to the variable Thus if a procedure is invoked recursively or by several turtles at once then each invocation has its own set of local variables which though they have the same name are kept distinct There may be any number of parameters on a TO statement
29. any procedure can call any procedure When the procedure calls itself we have a very powerful logical structure called recursion One clever example of recur sion was given by Hofstader in his book Godel Escher Bach There are actually two types of recursion Well start with the easier one recursion where the call is the last statement of the procedure As usual it is easiest to look at examples Recur sion can be used in place of the REPEAT statement TO CIRCLE FD 1 LT 2 CIRCLE END When we run CIRCLE the turtle moves forward one step and turns Then CIRCLE is called which causes the turtle to move forward one step and turn etc In principle this process could continue forever However every time a procedure is called some memory is used up Even tually the memory is all used up and we get the message MY MEMORY IS TOO FULL Try it So although recursion can be used instead of REPEAT in some procedures there are some dis advantages to doing this We have to find some way of stopping the computer or it will run out of memory There are also some great advantages to using this type of recursion The following program appears in all LOGO books and manuals TO POLYSPI SIZE ANGLE STEP FD SIZE RT ANGLE POLYSPI SIZE STEP ANGLE STEP END This procedure is so much fun to play with that we think you should do so before we get involved in any explanations One suggestion before you start the figures created are
30. binations The following are all legal words in LOGO FEW MANY DOG ALPHABET XXYYZZ RT 9 The leading quotation mark indicates that these are words The quotation mark is neces sary to distinguish a word from a procedure name but the quotation mark is not part of the word We have already used words as variable names in MAKE commands MAKE X 20 This shows that a word can have a value attached to it We will return to this point later These LOGO words already give some indication of the difficulty of dealing with words via the computer It is relatively easy to program the computer to distinguish meaningful numbers and mathematical expressions from nonsense but it is not possible to program a microcom puter to distinguish real words from nonsense combinations of characters Therefore in deal ing with words we are going to have to be more selective in our projects and we are going to have to supply the computer with restricted selected words to operate on if we are to avoid nonsense Computers do not understand enough about English for us to use a discovery learn ing approach to the English language In LOGO we call a series of words a list A sentence is a list but a series of numbers is also a list Elements of a list words are separated by spaces Lists are indicated by enclosing them in square brackets The SHIFT 5 SHIFT sequence produces the left bracket and the SHIFT 5 SHIFT sequence produce
31. bot tom four lines of the screen disappearing because these lines are reserved for text but the line will be drawn to the top of the screen No doubt it will take you several tries of CLEAR FD to hit the top exactly using the smallest possible number By now you re probably tired of drawing vertical lines It s time to turn the turtle Clear the screen by typing CLEAR then pressing ENTER and enter these commands FORWARD 40 RIGHT 90 to make the change more obvious enter FORWARD 50 RIGHT 90 FORWARD SO The turtle understands degrees If you are using Super LOGO with small children we have a suggestion There is now quite a bit of information gathered about the effective use of LOGO with small children LOGO is a language for experimentation not a language to learn by imitation of items from a textbook Resist any temptation to explain degrees to the child who does not already know about them The child will learn about degrees easily from experimenting with LOGO Again we soon get tired of typing RIGHT so we abbreviate RT Try RT 90 Think right turn for RT Now the turtle points down We re half way to drawing a rectan gle so let s finish it Enter FD 46 RT 96 and see if you can finish it Let s look at very important fact about turtle behavior Clear the screen enter RT 45 RT 45 This produces the same heading as RT 90 When the turtle is told to turn it turns that fa
32. by a complete set of rules What about going the other way could we write a set of procedures to transform pig latin into English There is no problem removing the AY from the end of each word But then what There is no set of simple rules which tells us whether or not to move a particular consonant back to the start 126 Something which is trivial for a child playing with pig latin is extremely difficult to program The decision is one which requires vast knowledge of English not a few rules As such it can not be programmed This illustrates some of the difficulty of computerized language generation Another popular exercise is the generation of random sentences As long as we give the com puter lists which are properly divided into nouns verbs etc the computer can generate sen tences which have the correct form In general they will be nonsensical which is one reason that children find them amusing The following procedure could be extended to form more complex sentences TO MADLIB N FT MAKE NOUNS SLUGS EELS RATS MAKE NOUNS NOUNS ELVES MOMS MAKE VERBS CRAWL SWIM BITE MAKE VERBS VERBS DIVE LOVE PICKRANDOM NOUNS MAKE N RESULT PICKRANDOM VERBS PRINT SE N RESULT REPEAT 2500 FT MADLIB END You can execute this simply by entering MADLIB in RUN mode Extension of this to three word sentences of the form noun verb noun could be used to introduce the idea of transitive and intransitive verbs
33. cal operation in a control statement control statement 15 one which controls the sequence of operations in the procedure for example an IF or a REPEAT Turtle 0 uses a turn to create turtle 1 and then the computer gives turtle 1 a turn Next it is turtle 0 turn again and it creates turtle 2 then the computer gives turtles 1 and 2 each a turn Next turtle 0 uses its turn to create turtle 3 and the computer gives turtles 1 2 and 3 each a turn Again it is turtle s turn and it encounters the END Turtle 0 is now waiting for something to do We have not given turtle 0 anything else to do so it is waiting for a command from the keyboard If we press a command for turtle 0 to do nothing then all the other turtles get another turn Try it Of course we do not always want to have to sit at the keyboard pressing ENTER We can get the whole thing to work as planned if we give turtle 0 some procedure to run as well Try TO TESTI HATCH 1 BOX 50 30 60 HATCH 2 BOX 40 180 40 HATCH 3 BOX 60 100 20 BOX 20 150 120 END The last call of BOX has no HATCH preceding so it is addressed to turtle 0 That s more like it If you want to see in a bit more detail what is actually happening you might want to slow down the speed You can slow any procedure by inserting a SLOW command TO TESTI SLOW 30 HATCH 1 BOX 50 30 60 HATCH 2 BOX 40 180 40 HATCH 3 BOX 60 100 20 BOX 20 150 120 END The number after SLOW tells the computer how much to slow
34. down The number must be between 0 and 127 Zero is full speed and 127 is the slowest speed The SLOW command sets a speed for all procedures which will remain unchanged until reset with another SLOW com mand or until RUN mode is exited and then reentered TRACE is not as useful here because it is not always obvious which turtle is running the line displayed at the bottom of the screen Before we leave this example notice that at the completion of each turtle s procedure the tur tle disappears so that at the end only turtle 0 remains 78 course we use different procedures for the various turtles Try TO TEST2 HATCH 1 BOX 50 30 60 HATCH 2 BOX 40 180 90 HATCH 3 BOX 60 100 20 HATCH 4 CIRCLE 3 30 140 HATCH 5 CIRCLE 4 180 120 CIRCLE 5 90 90 END This procedure can be used to point out one potentially troublesome point What if we altered the procedure by making the procedure for turtle 0 BOX say BOX 80 90 90 If you try this you will find that the circles are not completed and that the two turtles drawing the circles remain on the screen This is because turtle 0 runs out of commands before the others are fin ished To avoid the problem always put the procedure for turtle 0 last and assign turtle 0 the most complex procedure Another solution to the problem mentioned above is contained in the procedure ABSTRACT TO ABSTRACT CLEAR DRAW COLORSET 1 RT 25 HATCH 1 PATH 1 4 30 RT 43 HATCH 2 PATH 2 4 20 RT 67 HATCH 3 PAT
35. dure by starting the first line with the keyword To name this first procedure RECTANGLE enter TO RECTANGLE Procedure names must fit on a single line must contain no spaces and must not be the same as any of the keywords or abbreviations for example REPEAT FORWARD or FD The word TO must begin in column 1 If you made a typing error when you were using RUN mode you got the error message DON T KNOW HOW followed by your mistyped command Because a procedure name can be almost anything the computer assumes that any characters which don t form a correct keyword must form a procedure name If the characters are really a typing error then the name is not found in the list of procedures and the error message is sent Next type in the turtle commands for drawing the rectangle That is type FD 50 RT 90 FD 30 RT 90 FD 50 RT 90 FD 30 Many commands can be typed on a single line as long as they are separated by one or more spaces To finish the procedure type END on a new line and press ENTER To try out RECTANGLE you must leave EDIT mode by pressing the BREAK key and then get into the RUN mode by pressing the R key To actually run the procedure type RECTANGLE and press ENTER 19 That s neat that we should try it again again enter the procedure name at least three more times Now the screen should show By placing the procedure RECTANGLE in th
36. is clear that while much is possible with the turtle shapes Super LOGO is not likely to become a tool for the generation of Saturday morning TV shows It was never intended that it should be so It is a tool that will allow the child to produce results which can be immensely satisfying to the creator 96 18 TURTLE GAMES One of the most popular applications of computers is gaming Super LOGO can be used to cre ate a great variety of games In this chapter we will give two examples of turtle games These are included not as competitors for the local video arcade but as illustrations of some very useful techniques for communication between turtles Before getting into the details of the simple game going to use we want to point out a few things which may be obvious Most of the popular video arcade and computer games rely very heavily on speed Things happen which force the players to react faster and faster until finally they fail You ve already gotten some feel for the speed at which animation runs in Super LOGO it s not going to be fast enough to create shoot em up space games that will hold Interest for long However it does have capabilities such that the user can create rather than just play such games If you want to create games which will also be challenging to play using Super LOGO then you might try to think of games where coordination of several moving objects is the challenge thus lower speed is no limitation or games w
37. likely to outgrow the screen long before the memory runs out The wrap around feature of the screen will then lead to some striking but puzzling effects To start with let s prevent wrap around Enter RUN mode and type NOWRAP 45 Then try a variety of runs for example DRAW CLEAR POLYSPI 1 90 1 DRAW CLEAR POLYSPI 1 90 5 DRAW CLEAR POLYSPI 1 120 3 DRAW CLEAR POLYSPI 1 122 3 DRAW CLEAR POLYSPI 1 144 5 DRAW CLEAR POLYSPI 1 145 1 DRAW CLEAR POLYSPI 1 176 3 pPoLvYSPI 1 144 5 If you then want to see what happens when the computer allows wrap around type WRAP and try some more runs Now let s try to figure out what is going on with this POLYSPI It is useful to think of a Super LOGO program terms of levels the main program 15 a procedure at level 0 subprocedure called from level 0 is at level 1 a subprocedure called from level 1 is at level 2 etc The operation of a program like MANY be diagrammed as follows Level O MANY Level FOUR T Level 2 BOX 46 transitions down up between levels 0 and 1 controlled by the statement in MANY down to level 1 and the END statement in FOUR up to level 0 The transitions down and up between levels 1 and 2 are controlled by the REPEAT 4 statement in FOUR down to level 2 four times and the END statement in BOX up to level 1 In a program like POLYSPI the path is actually less complex Level O POLYSPI Level POLYSP
38. list of dice to be rethrown is a Super LOGO list Therefore in typing the numbers remember to leave spaces between them Once all the required procedures are present you can execute DICETHROW simply by enter ing DICETHROW in RUN mode For our next example we use a variation of the word search game based on dice The differ ences are that the faces of the dice show letters instead of numbers and that the order in which the individual dice are thrown matters too The objective is to produce a randomly selected and arranged square array of letters The players are then to pick words from the array using adjacent letters Of course the computer cannot be programmed to decide if partic ular combinations of letters form real English words so we will just produce the square of letters and leave the rules of the rest of the game to the players We could pick a square of any size but 4x4 gives enough variety 150 Each die shows six letters The letters be picked in any fashion but we won t get much variety if we make all the dice the same Ideally the letters on the 16 dice should be selected to correspond to the frequency of occurrence of those letters in English TO HIDEWORD FT HATCH 1 DICE N I D U T K HATCH 2 DICE R A C L T E HATCH 3 DICE IM D R A N T HATCH 4 DICE N A G O S V HATCH 5 DICE O C A S E U HATCH 6 DICE E M R D A C HATCH 7 DICE D I S T W HATCH 8 DICE B T L Y O E HATCH 9 DICE L G W P U O HATCH 1
39. pace A useful debugging method is to HATCH a turtle from RUN mode and tell it to run the procedure which is to be tested Then the procedure is run by pressing repeatedly If you enter a VANISH command then the main turtle will disappear and the hatched turtle will run at full speed ERROR MESSAGES FROM SUPER LOGO In BREAK mode a is printed if any key other than a valid command letter is pressed A load or save command may also print a digit followed by a These messages are 1 memory error 2 tape checksum error probably a bad tape or the volume not set correctly 3 attempt to load a tape that is not a Super LOGO program 4 attempt to load a module that is too long for memory In RUN mode there are several possible messages that may be issued These messages attempt to identify the error in the program but remember that the message is only a guess as to what is wrong It is possible that the message does not exactly fit the problem If the statement in error is from within a procedure then the line in error is displayed after the error message After one of the following messages is displayed the user must press a key to continue MESSAGE PROBABLE MEANING I DONT KNOW HOW is filled in with the name of what Super LOGO thought was a procedure name to call but the proce dure name is not found in the program area If the name is one which should be in the program area make sure that it is preceded by TO not
40. poll the keyboard forever There are certain features of Super LOGO which make this part of the programming very simple By assigning one turtle the task of watching the keyboard at all times we make sure that the two players have equal access to control we are very unlikely to lose keystrokes while something else is happening and provision for regular polling of the keyboard is handled automatically by the logic which handles multiple turtles Now let s turn our attention to RUNNER TO RUNNER X PU SX X SHAPE FFFFFFFFUBBBRRFD FFUBBBDBBB WHILE 1 1 MAKE X MAIL 1 IF X IF X 1 FD 8 ELSE RT X END RUNNER sets a starting position for the runner lifts the pen so that the runner leaves no tracks which makes no difference in the chase but keeps the screen clean and draws a shape so that the runner will look different We then enter another WHILE 1 1 which will run forever 99 The runner turtle now checks its mailbox by using the MAIL function The number following MAIL the argument is the number of the turtle that the runner turtle will accept mail from Here turtle 2 the runner turtle is asking for mail from turtle 1 the keyboard turtle If there is no message then MAIL returns the value 0 The statement IF X checks for the value of X If it is 0 then the statements in parentheses are skipped Since the parentheses enclose all the rest of the commands a 0 causes the loop to start again Thu
41. question our suggestions and don t hesitate to try out new ideas Perhaps the best way to start with very young children is to let them play By play we mean allow them to explore the effects of the various keys If the children are very young this will take quite a bit of time If you ve changed the shapes available in the OK Set since the last session then you should give the child another chance to explore the new set of keys Keep in mind that a child s attention span is not as long as yours so don t try to prolong the sessions Our own first ideas for Color LOGO grew from an effort to create something for a four year old to do because he wanted to be like Dad and work on the computer This suggests that another way to start is to master DOODLE mode yourself and to prepare a set of procedures for the OK Set Then you ll be ready when an interested face appears at your shoulder some evening The users of LOGO have had consistent success with one technique for getting children started They repeatedly relate the turtle commands with body movement That is ask the children to play turtle and ask them to keep track of the turtle movements they make Thus if the task is to draw a box the child is asked to walk in a box shaped path and then to tell the turtle what he or she did The success on which this recommendation is based comes from work with somewhat older children so it may not be quite as effective with the pre reading gr
42. the capacity of memory Note that a list created by a MAKE instruction within a procedure must fit on a sin gle line but a list entered from the keyboard is not subject to this limitation While entering a list you can backspace to correct typing errors only within a word once a space has been entered the preceding word cannot be changed The REQUEST function abbreviated RQ is identical to the READLIST function The following procedure gives a simple example of the use of RL TO GREET NAME FT PRINT WHAT IS YOUR MAKE RL PRINT SE WELCOME NAME END WHAT IS YOUR NAME RALPH WELCOME RALPH Let s make this a bit more elaborate TO GREET2 NAME FT PRINT WHAT IS YOUR MAKE WORD FIRST RL PRINT SE SE WELL NAME GLAD TO MEET YOU END WHAT 15 YOUR NAME VAL ERIE WELL VALERIE GLAD TO MEET YOU Here we want to use the name within a sentence Notice the double use of the SE function to combine the three pieces Also notice the command MAKE NAME WORD FIRST RL This takes the name from the keyboard and adds a comma to it FIRST is needed because RL produces a list FIRST takes the first and only word from that list and treats it as a word If we tried to add a comma to the list for example with the SE function there would be a space between the name and the comma If we omit the FIRST function we get an error message because we can t make a word from a list and
43. to load Super LOGO into your Color Computer system You will want to have some way to store your favorite creations for future display so you will want to have a cassette recorder attached to your computer system Consult the chapters on installa tion and operation in your copy of the Color Computer Operation Manual that came with your computer system for instructions as to proper cable connections for the cassette player DO NOT TURN ON THE POWER YET Loading Super LOGO Using a Color Computer Cassette System 1 With the computer s power off plug the Super LOGO cartridge into the slot on the right side of your Tandy Color Computer Check that the label is up and that the cartridge is seated firmly 2 Turn power on The computer power switch is on the back left corner of the computer The screen will display the prompt SUPER LOGO COPYRIGHT 1984 LARRY KHERIATY amp GEORGE GERHOLD LICENSED TO TANDY CORP ALL RIGHTS RESERVED LOGO Now turn to Using the Super LOGO Program on page 6 Using the Super LOGO Program You should now be in BREAK mode which is indicated by the prompt which ends LOGO at the left of the screen When you are in any other mode you can return to BREAK mode at any time by any one of three actions 1 If you press the key whatever you are doing will be interrupted and the com puter will return you to BREAK mode If a procedure a program that you have written in LOGO is actually running you must pr
44. tur tle here to turtle 2 Thus the inner part of the procedure says to continue checking mail and making moves as long as the runner is more than 12 steps away 100 If the runner is not more than 12 steps away then turtle 3 the sends message 1 to the scorekeeper turtle 0 Having sent the message the chaser returns to the home position and the chase begins again Now we turn to the procedure for the scorekeeper TO SCOREKEEPER S HT SX 200 SY 180 WHILE 1 1 PRINT CHAR 32 CHAR 32 PRINT S WHILE MAIL 255 0 MAKE S S 1 END Again there are several new ideas in this procedure The first steps are to hide the turtle and to position it to keep the scoreboard We set the initial score to 0 by the call of the procedure and again use a WHILE 1 1 to keep this turtle keeping score forever The PRINT statement causes what follows to be printed on the screen at the current turtle position The turtle is not moved However we want to print spaces to erase the old score and LOGO uses the space to indicate the end of something Therefore to print spaces we must use the CHAR function The CHAR function returns whatever character in the ASCII convention corresponds to the num ber in parentheses CHAR 32 gives a space To put two sets of characters together here two spaces together we use the concatenation operator Thus the combination CHAR 32 CHAR 32 gives two spaces The PRINT statement also can be
45. we can add the type of turtle commands we are already familiar with For example for a box with sides of length 40 we might use an RT 45 or RT 135 followed by an FD 60 This shows that DOODLE mode turtle commands can be mixed with regular turtle commands However in some sense this way of editing defeats the purpose of DOODLE mode because the child is not likely to be able to understand the change To keep it understandable for the child we edit using the DOODLE mode symbols in EDIT mode Each DOODLE mode symbol be made by pressing followed by the appropriate key Thus we could insert the above instructions for a diagonal by the series of keystrokes 5 8 2 8 0 8 0 8 0 8 8 That 45 5 followed by six FD 10 s 8 Try it Obviously this kind of editing would be most useful in a cooperative project where the child was using DOODLE mode and the helper was using EDIT mode A more likely type of error correction or editing is to make changes during the doodling process For example I should not have taken that last step forward or I should not have turned that far To see how to handle this get into DOODLE mode R and enter a new name say B Now doodle out a box but go one step too far on the last side Left arrow backspace will now erase the last step in the procedure Note that it does not erase the symbol for that step from the list at the bottom of the screen Try elimina
46. 0 DICE A H Y F E HATCH 11 DICE B K O F RJ HATCH 12 DICE D V N Z E A HATCH 13 DICE J E B R HATCH 14 DICE O P A N T H HATCH 15 DICE Y EG U K L HATCH 16 DICE L UP A T S REPEAT 2000 REPEAT 4 PRINT REPEAT 4 PRINT CHAR MAIL 255 PRINT CHAR 32 END f This procedure uses multiple turtles to randomize the order in which the dice are thrown The results of each throw will be sent as mail to this master procedure the MAIL 255 reads them in the order in which they are sent regardless of the source The REPEAT 2000 isa delay to make sure that this master procedure does not start reading mail before all the other turtles have sent their results Without a delay MAIL 255 might return 0 in some cases Be cause the letters are to be sent as mail from the other turtles the letters must be sent in the form of numbers The obvious code for the letters is the ASCII code and the CHAR function converts these codes back into the letters The last two REPEAT statements cause the letters to be printed out in a 4 x 4 square The above paragraph pretty well defines what DICE must do It must select one entry from a list at random and send the ASCII code of the letter selected as a message to turtle 0 Note that DICE calls on the procedure NTOWORD which we saw in Chapter 23 151 TO DICE L A N MAKE A REPEAT 6 NTOWORD ASCII FIRST L MAKE A SE A RESULT MAKE L BF L REPEAT RANDOM 50 PICKRANDOM
47. 60 RT 30 FD 18 RT 130 FD 18 RT 32 FD 60 END 155 TO LITTLEHAND HOUR MINUTE SX 128 SY 96 SH 30 0 MINUTE 2 32 FD 30 60 FD 30 RT 120 30 60 FD 30 END TO DIGITAL HOUR MINUTES SX SY 180 PRINT CHAR 32 PRINT CHAR 32 PRINT CHAR 32 SX 8 lt 9 amp HOUR lt gt 790 IF HOUR PRINT HOUR ELSE PRINT 12 SX 16 PRINT SX 24 IF MINUTES lt 10 PRINT 0 SX 32 PRINT MINUTES END Notice that you can set the interval to any number of clock minutes and that you can set the speed with DELAY Try running CLOCK 300 5 156 Next we give another colorful design TO SPIDER X COLORSET 1 BG REPEAT 36 HATCH 1 OFFSET X C MAKE C C 1 RT 10 VANISH END TO OFFSET LENGTH COLOR PC COLOR FD LENGTH LT 30 FD LENGTH RT 30 FD LENGTH END Try this with SPIDER 45 157 Next we give one which will remind you of the start of every science fiction film you ve ever seen There is no picture in the manual for this one as the effect is all in the motion 158 TO SPACETRAVEL DRAW COLORSET 1 BG 0 HT MAKE X 4 WHILE 1 HATCH 1 STARI RT 67 HATCH 1 STAR2 RT 207 HATCH 1 STARI RT 114 HATCH 1 STAR2 RT 87 SETX XLOC ME X IF NEAR 255 gt 30 MAKE X X 1 HATCH 1 PLANET VANISH END TO STARI HT SHAPE FFRRFRRF PU FD2 ST REPEAT 25 FD 3 END TO STAR2 HT SHAPE F PU FD2 ST REPEAT 35 FD 3 END TO PLANET HT IF XLOC ME 128 SETH 75 ELSE S
48. A 6 SEND 0 RESULT END We first convert each letter to its corresponding ASCII number and convert that number to a word The list then contains the ASCII numbers for the letters the original list Next we put m a random delay REPEAT RANDOM 50 so that it is unpredictable when each of the 16 turtles returns its message to the queue of messages for turtle 0 Finally we pick a random entry off the list and send it as a message PICKRANDOM and its subprocedures are Chapter 22 I Z Fi A ey See A F kal With this example we complete the tutorial on list processing You may have noticed that in the last several chapters we have not introduced much in the way of new Super LOGO fea tures Instead we have been making new combinations to solve a variety of problems This is because we have all the features we need at hand solving new problems is mainly a process of analyzing and ordering the solutions That we will leave to you 152 27 GRAB BAG In this last chapter we return to graphics and give a final set of sample programs which we hope will give you ideas for your own projects We have introduced all the features of Super LOGO earlier so we will give these without lengthy comments The first set is controlled by the procedure BOND TO BOND WHILE 1 COLORSET 1 CLEAR HT DELAY 1000 TUNNEL WALK PAINT END TO WALK SX 28 MAN2 ST DELAY 2000 REPEAT 29 MAN2 DELAY 100 HT SX ME 3 MAN1 ST DELAY 100
49. ABSOLUTE BSOLUTE The abbreviation for BUTFIRST is BF Combinations of the two functions can be used to select any letter in a word The following combination will select the third letter PRINT FIRST BF BF ABSOLUTE 5 Notice that the order of operation is from right to left Compare the result with the sequence PRINT BF BF FIRST ABSOLUTE Here the function FIRST is done first returning the letter A The BF function then returns the empty word and the end result is a blank 108 We have similar set of functions for working on the end of a word Try PRINT LAST ABSOLUTE E and PRINT BUTLAST ABSOLUTE ABSOLUT and PRINT LAST BL BL ABSOLUTE U So we have a set of functions for pulling words apart You might have guessed that we have a function for building words too The WORD function combines two words into a new word Try PRINT WORD SNOW BALL SNOWBALL and PRINT WORD WORD SNOW BALL ED SNOWBALLED These are the primitive functions for words Remember that a word can be as short as a single letter or even an empty word Note In RUN mode a list processing command cannot be longer than one line Most of these same functions can be used on lists Try PRINT FIRST ONE TWO THREE ONE Notice that the result of the FIRST function ONE is the first word from the list Therefore the command PRINT FIRST FIRST ONE TWO O will return the word O Try the other commands as well PRIN
50. An Invitation to the Art and Pattern of Nature by David Thornburg Addison Wesley Publishing Co 1983 and the references therein Here we ll settle for writing proce dures to generate the series We need a subprocedure to convert a number to a word In Super LOGO the computer recog nizes when a word needs to be converted to a number by context one cannot add the charac ters one zero to another number but one can add the number ten However the computer does not make the conversion in the other direction automatically In true LOGO fashion when we discover that we need a new function we write a subprocedure to provide it TO NTOWORD NUM W W1 IF NUM 0 OUTPUT 0 MAKE W WHILE NUM gt MAKE W1 NUM MAKE NUM INT NUM 16 MAKE W WORD CHAR 1 0 gt 10 48 W OUTPUT W END This subprocedure uses the INT function to make the result of division an integer The differ ence between a number and ten times the integer portion of the number divided by 10 is the units digit NUM lt 10 units digit The CHAR function uses a number as its argument and returns a one character word which is the character which corresponds to that number in the ASCII sequence Because zero is character 48 and because the digits are assigned in order in the ASCII sequence the above CHAR function returns the digit selected as a word The subprocedure repeatedly divides by 10 to move digits to the right take
51. D RADIO SHACK shall not be liable for any damages caused by delay in delivering or furnishing Equipment and or Software No action arising out of any claimed breach of this Warranty or transactions under this Warranty may be brought more than two 2 years after the cause of action has accrued or more than four 4 years after the date of the Radio Shack sales document for the Equipment or Software whichever first occurs D Some states do not allow the limitation or exclusion of incidental or consequential damages so the above limitation s or exclusion s may not apply to CUSTOMER SOFTWARE LICENSE RADIO SHACK grants to CUSTOMER a non exclusive paid up license to use the TANDY Software on one computer subject to the following provisions A Except as otherwise provided in this Software License applicable copyright laws shall apply to the Software B Title to the medium on which the Software is recorded cassette and or diskette or stored ROM is transferred to CUSTOMER but not title to the Software C CUSTOMER may use Software on one host computer and access that Software through one or more terminals if the Software permits this function D CUSTOMER shall not use make manufacture or reproduce copies of Software except for use on one computer and as is specifically provided in this Software License Customer is expressly prohibited from disassembling the Software CUSTOMER is permitted to make additional copies of the Software on
52. D which completes the procedure at that level and goes up or by a call of another procedure which leaves the current procedure incomplete and goes down Instead of giving an elaborate account in words of what is happening we recommend that you run the program using TRACE and follow the table and the program in parallel If you get confused start over and try again Recursion is a little complex but it is so powerful that it is worth the effort to understand Incidentally the recursive call TREE 3 N 4 could be written TREE 0 75 just as well The first way is what is used with a system that only has integer arithmetic the second can be used with Super LOGO because it has two decimal arithmetic Two cautions if you use the second the zero before the decimal is essential and computer arithmetic is never very accurate in the last decimal no problem in this example You might think that the second way would be faster only one multiplication instead of a multiplication and a division but it isn t Most of the time is taken up in the bookkeeping for the recursion and for drawing the turtle many times The next program draws a figure which is called a fractal A fractal is a figure which looks the same no matter what magnification is used to view it of course we are limited by the screen resolution here In this example we ll start with the basic shape 222 50 The idea is that each of these four lines should be made up of t
53. E LLURRFFDBBLLFFFFFFRRR FFFRRRFFFFLFFUBBRBBBBRFFFRFD FFFFFFFFFRRRFFFFLLFF UBBLLFFFFLLFDFFFLLFU BLLFFFFLFDFLFRFFRFR FFRFRFFRFRF END Now that we have the shapes we can have some fun First let s make them walk TO WALK HT PU SX 100 RT 90 REPEAT 100 ONE ST WAITA 100 HT FD 6 TWO ST WAITA 100 HT FD 6 END TO WAITA T REPEAT T END Notice that in this case we want the turtle shape to be drawn at right angles to the turtle motion That is taken care of in the SHAPE statement Notice also that we have to slow down the process by including the WAITA procedure Otherwise it runs so fast that we have trouble seeing the shape Try other values for T to vary the speed We can make the figure climb just enter 15 before running WALK again We can even make the figure walk in a circle 92 WALK AROUND DRAW SX 100 RT 90 100 ONE ST WAITA 100 RT 15 FD 6 TWO ST WAITA 100 HT RT 15 FD 6 END You may prefer the motion you get with a different control procedure Try this as an alterna tive to WALK TO WALK1 HT PU SX 100 RT 90 REPEAT 100 HATCH 1 WALKA REPEAT 8 HT FD 6 HATCH 1 WALKB REPEAT 8 HT FD 6 END TO WALKA HT ONE ST REPEAT 10 END TO WALKB HT TWO ST REPEAT 10 END The trick here is to get the delays that is the REPEATS with empty parentheses synchro nized The delays in WALK1 must match with the delays in WALKA WALKB If
54. EAT 36 FD 10 RT 10 There are two advantages to using a smaller number of sides the circle is drawn faster and we can adjust the size of the circle in smaller steps Try REPEAT 36 FD 11 RT 10 REPEAT 36 FD 10 RT 10 REPEAT 36 FD 9 RT 10 REPEAT 40 FD 9 RT 9 12 Several geometry lessons could built around the examples given above There is usually little problem in getting the number of sides correct the number of times to repeat The chal lenge is to get the angle of the turn correct Let the user experiment with different angles until they get the correct angle After they have gotten a few correct see if they can general ize and predict the angle say for an 8 sided polygon an octagon It would be difficult to overstate the value of these kinds of activities They are much closer to the activities of mathematicians and scientists than what is usually taught in science and mathematics courses 13 4 5 AND EDITING New users of computers often find the idea of modes awkward Mode is the term used to describe the separation of the various things a computer language can do into groups There are a number of good reasons for having various modes One is that there are not enough different keys on the keyboard to control all the different things that need to be done The same keys can be used for different tasks in different modes without confusion at least on the computer s part The following diagra
55. ETH 300 FD 10 SHAPE FFRFFRFFRFFRFFR FFRFFRFF PU FD6 ST REPEAT 20 FD 4 END Here s which shows the orbit of a moon around planet which makes use of multiple turtles to simplify the mathematics TO ORBIT COLORSET 1 BG 0 FD 10 RT 90 PC 3 REPEAT 8 FD 6 RT 45 FD 6 HOME PU SETH 90 SY 164 MAKE MOONPOS 0 SHAPE 0 FFFFFRRDFFRFFFFRFFFFRFFFF RFFFFRFFFFRFFFFRFFFFRF WHILE 1 REPEAT 4 HATCH 1 MOON MOONPOS REPEAT 6 MAKE MOONPOS MOONPOS 20 FD 10 RT 9 END TO MOON POS HT PU RT MOONPOS FD 20 SHAPE UFFFFRRDFRFFRFFRFFR FFRFFRFFRFFRF ST REPEAT 9 VANISH END 159 our last example we give fimal pretty pattern TO SAMPLE COLORSET 1 DRAW BG 0 NPOLY 8 12 3 SX 76 SY 72 N2POLY 8 48 12 END TO NPOLY N S C PC C REPEAT N POLYGON N S RT 360 END TO POLYGON N S REPEAT N FD S RT 360 END TO N2POLY N S1 S2 l PU MAKE l 1 WHILE 1 lt N HATCH 1 NPOLY N S2 1 1 INT 1 2 2 FD S1 RT 360 MAKE 4 1 1 VANISH END Of course you can try this set with other inputs than those given in SAMPLE Well we have now reached the point where you are on your own We are sure that the exam ples herein have just scratched the surface of what is possible We hope that you have as much enjoyment working out your own demonstration procedures as we have had in developing these 160 APPENDIX LANGUAGE SUMMARY
56. FD N 4 RT 86 FD N LT 166 FD N RT 86 FD N 4 STOP and try DRAW FLAKE 150 52 Another variation 1s IF N 9 FD 4 RT 80 FD 2 N 160 FD 2 N RT 80 FD 4 STOP and try DRAW FLAKE 150 DRAW FLAKE 70 Recursion can be used to draw endless space filling patterns The following example is typical TO FOO SIZE LEVEL PARITY HT IF LEVEL 0 STOP LT PARITY 90 FOO SIZE LEVEL 1 PARITY 1 FD SIZE RT PARITY 90 FOO SIZE LEVEL 1 PARITY FD SIZE FOO SIZE LEVEL 1 PARITY RT PARITY 90 FD SIZE FOO SIZE LEVEL 1 PARIT Y 1 LT PARITY 90 END 53 An appropriate set of numbers is DRAW FOO 6 6 1 In this chapter we have tried to give you some ideas for recursive programs However we have Just scratched the surface of the designs that are possible Go ahead and experiment and let others know if you discover any new beautiful designs 54 12 DOODLE MODE PROCEDURES WITHOUT TYPING Super LOGO provides a way to enter graphic procedures into the computer without typing the turtle commands like FORWARD and RIGHT The reason for including this feature is to pro vide a way for children who are not ready to read or to type to use the language and to benefit from the practice in structured thinking that the language offers The features of DOODLE mode are arranged with that audience in mind Obviously the children are not going to be able to read the manual so a
57. First run this procedure FULLTEXT PHONEBOOK then enter commands like PRINT CHRIS PRINT CHRIS 114 computer will respond with the two lines CHRIS 555 9965 The first command PRINT CHRIS tells the computer to print the literal word CHRIS The second command PRINT CHRIS tells the computer to print the current value of the varia ble named CHRIS which is the phone number The command MAKE CHRIS 555 9965 in the procedure loaded the word 555 9965 into the memory space named CHRIS Remember that MAKE commands will always have a variable name a word followed by a value a word a number a list or an expression which evaluates to a word number or list In the examples in this chapter the values output and used as results have been numbers mainly because this minimizes the confusion between the name of the variable and the value it holds In following chapters we will see examples where the values can be words and lists as well 115 21 INTERACTIVE PROCEDURES Many list processing procedures procedures that manipulate words will be more interesting if they are interactive that is if the person running the procedure can feed information into the procedure from the keyboard while the procedure is running We ve already seen one way to do that the KEY function The KEY function is most suitable for writing game procedures because it checks the keyboard and then continues imm
58. GAMES Dice games provide further illustrations of list processing and they provide a rich source of interesting projects Many games are based on throwing multiple dice Some of them allow you to select some dice for rethrowing thus allowing you chances to improve the result Instead of picking a particular game we will just give the dice throwing procedures For purpose of illus tration we will assume that the games use five dice and that the games allow rethrow of selected dice two times The main is called DICETHROW Note You may want to MERGE i in S IK HEY that you created in Chaar 22 df they are not already in n memory Many of them will used in this chapter 0 DICETHROW SET REDO FT MAKE SET REPEAT 5 THROW MAKE SET SE SET RESULT REPEAT 2 PRINT SET PRINT LIST DISCARDS MAKE RL IF REDO lt gt DIFFERENCE REDO SET MAKE SET RESULT LENGTH SET MAKE 5 RESULT REPEAT N THROW MAKE SET SE SET RESULT PRINT SE FINAL HAND 5 END There are really no new techniques used in this procedure The subprocedure TH ROW is used to actually throw the dice the subprocedure DIFFERENCE is used to eliminate the words in the list REDO from the words in SET To function properly here DIFFERENCE must elimi nate only one occurrence in SET not every occurrence LENGTH is a subprocedure given in Chapter 22 which returns the length of a list THROW picks one number fro
59. H 3 4 40 RT 105 HATCH 4 PATH 0 4 10 VANISH END Notice the RT commands to turn turtle 0 between each HATCH The initial position and heading of each new turtle is the same as that of the parent turtle the turtle which hatches the new one In this example turtle 0 is the parent so each new turtle will have the position and heading of turtle 0 at the time of HATCHing After the four new turtles are created then turtle 0 is given the VANISH command The VANISH command tells a turtle to go out of ex istence Once turtle 0 is out of existence it no longer gets a turn and it cannot bring the procedure to a halt by running out of commands 79 Of course the procedure ABSTRACT needs PATH to function TO PATH COLOR I L HT PC COLOR WHILE 1 1 FD L RT 90 PU FD l RT 90 PD FD L LT 90 PU FD I LT 90 PD IF NEAR 255 gt 156 RT 168 END PATH contains some new ideas which we should explain The first is the WHILE statement The WHILE is somewhat like a REPEAT but with a condition The most common use is to repeat while some condition is true for example WHILE X lt 3 The computer evaluates the condition and returns the value zero if the condition is false or a non zero value if the con dition is true Here we want it to repeat forever so we assign the condition 1 1 which always is true The parentheses following the WHILE enclose the commands which are to be repeated The other new idea is the use of the NEAR function The
60. HT PD REPEAT 66 FD 8 BK 8 RT 6 PU ST END All these procedures restore the turtle to its starting position It is not always easy to compute what moves are necessary to reach the original position In T we did it by experiment Run T immediately upon entering RUN mode so that the starting position for the turtle is at the home 128 96 position When the procedure has finished enter the line PRINT XCOR 60 This tells the computer to print out the x coordinate of the turtle position Since we started at home we want to end at home which has an x coordinate of 128 Notice that the printing occurs at the position of the turtle without moving the turtle Therefore we can follow this with the command PRINT YCOR to see that we ve returned to the correct vertical position as well Of course the procedure T is correct we showed you this in case you wanted to define procedures for other shapes as well From these values we could tell what changes would have to be made in the last line of T to restore the turtle to the original home position With these procedures the child can move the turtle around the screen using the number keys and the child can produce triangles by entering T boxes by entering B and circles by enter ing C But we hear you say this is for children who don t know the letters We suggest that you cover the selected keys with small adhesive labels on which the symbols have been drawn In this example this would mean pu
61. I Level 2 POLYSPI Level 3 POLYSPI The transitions down are controlled by the statement POLYSPI SIZE STEP ANGLE STEP There are no transitions back up because the procedure never reaches the END statement Thus the computer sinks down level after level until it finally runs out of memory POLYSPI gives interesting figures because of the difference in the values of the variables at the differ ent levels We begin the program with the command POLYSPI 1 90 5 Level The recursive call of the procedure is when we substitute the current values of the variables POLYSPI 6 90 5 Level 1 Therefore at level 0 the FD command is for length 1 and at level 1 the FD command is for length 6 The pattern continues POLYSPI 11 90 5 Level 2 POLYSPI 16 90 5 Level 3 until the turtle runs off the screen or the computer runs out of memory We now turn to the more complex type of recursion recursion where returns to the higher levels are actually made Another popular program in turtle geometry is called TREE TO TREE N IF N 2 STOP FD N RT 15 TREE 3 N A LT 30 TREE 3 N A RT 15 BK N END OO 1 FP WN 47 line numbers not of the procedure they there for reference im our discussion of the procedure Enter this procedure without the line numbers of course and try running it with a value of 20 to 30 for N You might try making the numerical factors in the two calls
62. NEAR function returns an indication of the distance from the current turtle to the designated turtle Actually what you get is the total of the steps in the x direction and in the y direction to the designated tur tle In PATH the statement is IF NEAR 255 gt 150 RT 108 The current turtle remember 1 2 3 or 4 is asking the distance to turtle 255 But turtle 255 does not exist When you request the distance to a non existent turtle you get the distance to the home position Therefore this statement says if the current turtle is more than 150 steps away from home then turn right 108 degrees After such a long explanation we should get a program which runs a long time ABSTRACT will surely fit the bill it will run until you hit the BREAK key or until there is a power failure 80 Perhaps you d like a different design TO MIXIT DRAW COLORSET 1 BG 0 HATCH 1 SWEEP 13 60 30 0 HATCH 2 SWEEP 23 60 160 90 HATCH 3 SWEEP 3 3 190 160 180 HATCH 4 SWEEP 2 3 190 30 270 VANISH END TO SWEEP COL INT X Y H REPEAT 12 HT PC COL SX X SY Y SH H REPEAT 92 INT PD FD 100 PU BK 100 RT INT MAKE COL COL 1 END There is no question that the turtles slow down as the number of turtles on the screen increases After all more is going on Thus far we haven t had so many that the slowing is that noticeable But how about a program which generates a lot of turtles One interesting test is to return to a recursion progr
63. OF SUPER LOGO FOR THE TANDY COLOR COMPUTER STARTING LOGO From plug in With the computer power off plug the Super LOGO cartridge into the ROM pack game slot Then turn on the computer MODES IN SUPER LOGO The Super LOGO system can be in one of four modes depending upon what the user is doing at the time brief explanation of each is given here BREAK MODE is entered upon system startup and any time the user presses BREAK must be pressed twice to interrupt a procedure and enter mode In this mode the user can load and or save programs from tape make printed copies of programs or enter EDIT or RUN modes EDIT MODE To get into this mode from BREAK mode press the E key In this mode the user can view create or modify programs RUN MODE To get into this mode from BREAK mode press the R key In this mode the user can enter turtle commands call programs to be run or enter DOODLE mode DOODLE MODE To get into this mode press the key when you RUN mode In this mode the user can use specially marked keys to doodle a picture while creating a procedure 161 BREAK BREAK mode is entered automatically upon starting Super LOGO and be entered from any other mode by pressing the BREAK key at any time It is signified by the LOGO prompt on the screen The following single letter commands may be used in BREAK mode SHIFT CLEAR clears the internal program area gets you into RUN mo
64. Once we have taught the turtle new word writing procedure we use that new word In other procedures Return to EDIT mode and remove the commands for drawing the diagonal we used RT 122 FD 59 from BOX Now move to a new line press In fact a blank line between procedures will help keep things easy to read so press again We re going to write another procedure to draw the pattern of four boxes We ll call it FOUR so type TO FOUR BOX BOX BOX BOX END Notice that we ve used BOX as a turtle command in the same way that we used FORWARD and RIGHT within BOX Run FOUR to see that it works The result is the same as that shown on page 20 To run the procedure FOUR the computer must have available the subprocedure BOX Both procedures must be in the program space when FOUR is run but their order within that space is of no importance We could have written FOUR first and then written BOX with exactly the same result The procedure FOUR can be shortened by use of the REPEAT control statement The altered form of FOUR is TO FOUR REPEAT 4 BOX END The space after the number 4 is optional The parentheses can include a whole list of turtle commands and subprocedure names The list in parentheses can extend over many lines but the parentheses are essential Now that we have taught the turtle what FOUR means we can move to a higher level proce dure Try TO MANY REPEAT 10 FOUR RT 9 END 23 You ar
65. T 7 SX X SY Y SQUARE MAKE Y 20 MAKE X 20 MAKE Y 50 MAKE X 11 MAKE Y 58 REPEAT 4 REPEAT 5 SX X SY Y T MAKE X 40 MAKE X 11 MAKE Y 40 SX 31 SY 158 ST END TO SQUARE REPEAT 4 FD 20 RT 90 END 66 Lun ees The child s task is to complete the pattern by moving the turtle and by pressing the key with the triangle Many other variations on this theme are possible The PATTERNS procedure makes heavy use of the MAKE statement and we have not dis cussed that before The MAKE statement changes the value in the memory space referred to by the variable name following the MAKE to the value given by the next expression or num ber For example MAKE X X 40 replaces the starting value in the memory position named X name X indicated by X with a value which is 40 greater than the current value Notice that LOGO distinguishes between the name of the variable and the contents of the variable X Not all versions of LOGO make this distinction so Super LOGO also accepts the syntax MAKE X X 40 Of course not all the tasks using the triangles squares and circles need to be directed towards specific goals Ask the child to create a design or to create a border to the screen Another group of projects can be based on completion of design The screen can be thought of as consisting of four quadrants divided at the home position The idea is t
66. T BUTFIRST A B C D B C D PRINT LAST A B C D D PRINT BUTLAST A B C D ABC 109 Obviously combinations be used they were used with words to pick out word from a list Words are combined into lists by the SENTENCE function Try PRINT SENTENCE SNOW BALL SNOW BALL Contrast the result here with the result using the WORD function SNOWBALL SENTENCE produces a list WORD produces a word Lists can be combined and words and lists can be combined We ll use the abbreviation SE for the SENTENCE function PRINT SE SLOW BOAT TO CHINA SLOW BOAT TO CHINA The functions FPUT and LPUT also can be used to combine a word and a list to form a new list and the function LIST also can be used to form a new list from two words They are included for compatibility with other implementations of LOGO but we ll stick with SENTENCE in our examples see Appendix I for more information This completes the introduction of the primitive word and list functions Notice that these are functions which produce a result which is not visible on the screen unless printed This is different than turtle graphic primitives which produce visible results automatically To make full use of these new primitives we ll have to learn to pass the results between subprocedures and procedures 110 20 COMMUNICATION BETWEEN PROCEDURES Thus far all our procedures have produced graphics Graphic procedures produce figures or patter
67. T FD 12 END TO BIGDOT FD 1 RT 90 FD 1 REPEAT 4 RT 90 FD 2 PU 1 90 BK 1 END We could have used the LOGO primitive DOT a predefined LOGO command described on page 172 instead of BIGDOT but later on we ll want to be sure that the dot is centered on the starting point Note that we could not use the name DOT instead of BIGDOT for the procedure for the computer would use the primitive instead of the procedure Next we draw some very simple repeating pattern on the upper row of dots We ll use DOTS in the pattern drawing procedure Several examples follow 1 DOTS SX 5 SY 150 REPEAT 10 PD FD 12 PU FD 12 SX 5 SY 50 ST PD END Try running PATTERN1 The idea is that the child is to reproduce the pattern of the upper set of dots on the lower set and then after that is mastered the child is to give an equivalent pattern with some other shapes Before you try this with a child try it yourself Try to copy the pattern on the lower row of dots You ll find that it is more difficult than necessary It is needlessly difficult to move the turtle the correct number of units 12 as the procedure is writ ten We can make the exercise much less bothersome by some minor adjustments Notice that these adjustments in no way detract from the point of the exercise which is to recognize and continue the pattern TO LINE OF DOTS REPEAT 12 BIGDOT FD 20 END change to FD 20 means that the child
68. T mode When entering commands you can use the left arrow key lt to erase the last command In this case the entire screen is erased and the shape is re drawn without the last entered com mand To exit the DOODLE mode press procedure created in DOODLE mode can be called out from RUN mode to re draw the picture again To do so just enter the name that was given when DOODLE mode was entered The DOODLE mode commands are 1 CLEAR 2 HOME 3 PU 4 PD 5 RT 45 6 LT 45 7 FD 1 8 FD 10 9 RT 15 0 LT 15 SPECIAL CHARACTERS The characters and are not on the keyboard However these characters are used in Super LOGO To enter a hold down and press 5 followed by and then 8 Similarly to enter hold down SHIFT and press 5 followed by and then 9 The square brackets and must be used in conjuction with entering a LIST of words Another possible use of these characters is in the grouping of statements after an IF ELSE REPEAT or WHILE In these cases either parentheses or brackets may be used inter changeably To enter a character hold down SHIFT and press 5 twice 167 SUPER LOGO STATEMENTS COMMANDS CONTROL STATEMENTS In the statements below the list of statements referred to may be enclosed or sym bols The symbols provide compatibility with Color LOGO The symbols provide com patibility with other LOGOs END This is the last statement in a procedure E
69. TANDY Cat No 26 2717 LOGO Creative Programming and Graphics for the Color Computer TERMS AND CONDITIONS OF SALE AND LICENSE TANDY COMPUTER EQUIPMENT AND SOFTWARE PURCHASED FROM RADIO SHACK COMPANY OWNED COMPUTER CENTERS RETAIL STORES AND RADIO SHACK FRANCHISEES OR DEALERS AT THEIR AUTHORIZED LOCATIONS LIMITED WARRANTY CUSTOMER OBLIGATIONS A CUSTOMER assumes full responsibility that this computer hardware purchased the Equipment and any copies of software included with the Equipment or licensed separately the Software meets the specifications capacity capabilities versatility and other requirements of CUSTOMER B CUSTOMER assumes full responsibility for the condition and effectiveness of the operating environment in which the Equipment and Software are to function and for its installation LIMITED WARRANTIES AND CONDITIONS OF SALE A For a period of ninety 90 calendar days from the date of the Radio Shack sales document received upon purchase of the Equipment RADIO SHACK warrants to the original CUSTOMER that the Equipment and the medium upon which the Software is stored is free from manufacturing defects This warranty is only applicable to purchases of Tandy Equipment by the original customer from Radio Shack company owned computer centers retail stores and Radio Shack franchisees and dealers at their authorized locations The warranty is void if the Equipment s case or
70. UE Then when the scrolling stops on a line containing BLUE the user could find the next occurrence by pressing SHIFT ENTER This could be repeated many times if needed BREAK exits EDIT mode and returns to BREAK mode allows the next character to be one of the specially marked single key command codes To enter a real press l twice In general to enter new lines just type each line followed by ENTER To modify a line move the cursor into place with the arrow keys then modify text by typing the new text over the old or by inserting or deleting characters as described above Note If the editor quits accepting new text then the program area is full The editor is general enough to be used not only for writing Super LOGO programs but also for simple word processing applications After you edit a text file the file may be printed or saved on disk or cassette for later use One such use would be writing documentation for mod ules written in Super LOGO Since the editor has a maximum line length of 32 characters a facility is provided to allow for printing of longer text lines on the printer If a line is ended with an 2 character then no RETURN is output at the end of the line The result will be that the following line on the screen will be printed on the same printer line 164 INTERNAL PROGRAM AREA Super LOGO procedures are entered in the EDIT mode They can then be saved on disk or tape and re loaded later
71. a character 120 We have now seen all the functions which be used to make procedures interactive Well end this chapter with a brief summary KEY RC RL or RQ PADDLE reads one key from keyboard as the ASCII number if it is depressed at the moment KEY is executed waits until one key at the keyboard is depressed and reads it as a word reads a list terminated by ENTER from the keyboard reads the position of one of the game paddles as a number between 0 and 63 121 22 PLAYING WITH WORDS AND SENTENCES One obvious application of the word and list functions is to generate and alter English words and sentences We quickly discover that English is very complex and that most projects are far beyond the capabilities of microcomputers In fact programming computers to understand nat ural language is an active research area on the largest current machines The experimental approach which is so effective in turtle graphics is not practical with sentences we do not dis cover much about English by trial and error with words and lists In this chapter we will ilhs trate some simple language procedures and in the next chapter we will give some examples of list operations which do not attempt to combine words as sentences We ll begin with some procedures which will be generally useful Often we want to pick a word from list either a designated word or one selected randomly The following procedure si
72. ake the circle smaller we try TO CIRCLE REPEAT 180 FD 1 RT 2 END That s more like it Next we need to fit a square around this circle One disadvantage of this way of drawing circles is that we do not know the size that is the radius of the resulting cir cle We can find it by experiment Simply run the CIRCLE procedure then turn the turtle right 90 degrees and move the turtle forward until it crosses the circle first guess of 50 seems about right When we try FD 50 we find that we need bit more and that the diameter of the circle 16 about 56 units It appears that we should then enter a procedure to draw a square with sides of 56 units TO SQUARE REPEAT 4 FD 56 RT 90 END 24 SQUARE This will draw a square but it will leave us with a problem SQUARE starts with the turtle at a corner of the square The corner is an awkward place to start drawing a square which is around a circle This example shows that when procedures are to be used together some atten tion must be devoted to making them fit or connect We choose to make the two procedures connect by starting and ending the square at the center of a side where the circle and the square touch TO SQUARE REPEAT 4 FD 28 RT 90 FD 28 END Now verify that this set of procedures is a solution to the original problem by running PATTERN Let s analyze what we ve just done The road map for attacking the problem was to break the problem into a set of subproblem
73. alled the turtle even when it is just a shape on the screen The graphics portion of Super LOGO is a language for controlling turtles We have a turtle in the center of the screen itching for action Let s tell the turtle to move for ward Simply type FORWARD 40 Then press ENTER The number after FORWARD tells the turtle how far forward to move After you enter FORWARD 40 the screen will show turtle track It won t be long before you get tired of typing FORWARD all the time so there is abbrevi ation which has the same effect Enter the following that is type it and press ENTER FD 10 Try to get a feel for the screen size and resolution Try FD 1 It s almost too little to see Then try with a larger number like FD 100 The turtle moved but it didn t leave a complete track When the turtle goes off the top of the screen it reenters at the bottom a process which is called wrapping around However at this stage we have the bottom four lines of the screen reserved for text so the portion of turtle track which passes through those bottom four lines does not appear Now let s find out how far it is from the center of the screen to the top To get a fresh start and a clear screen enter the word not the single key CLEAR Then try to make the turtle track go to the top of the screen with a single FD command When you have it exactly right the turtle itself will wrap around disappearing into the
74. am and implement it using multiple turtles TREE1 is an ideal example Try the following 81 TREE1 5 IF 0 CLEAR DRAW SETY 0 IF S gt 6 FD S LT 30 HATCH 1 TREE1 3 S 4 RT 60 HATCH 2 TREE 3 S 4 VANISH END TREE1 40 is an example that gives good results Again we ve introduced a new idea with this procedure here the ME function The ME func tion returns the identification number of the current turtle The statement IF 0 CLEAR DRAW SETY 0 says if the current turtle is turtle 0 then clear the screen use the full screen and move Because turtle 0 is subsequently told to VANISH this will happen only once This procedure recursively hatches new turtles all named either 1 or 2 Because the recursive calls keep levels distinct this is satisfactory but functions like NEAR would give unpredictable results because the various turtles are not uniquely named 82 There are number of interesting things that can be tried with this procedure One is to compare it in speed with the earlier version of TREE In one case you have all the backing up necessary for a pure recursive program and in the other you have the overhead necessary to keep track of all the turtles To make the comparison meaningful you ll have to make the two versions draw the same size tree but by now that will be easy The comparison may give some idea of why multiprogramming is worth learning about You can speed the multiple turtl
75. arer if it were typed as follows TO BOX FD 50 RT 90 FD 30 RT 90 FD 50 RT 90 FD 36 END These changes require us to break single lines into multiple lines To break a line position the cursor where you want to break the line hold the SHIFT key down and press the down arrow key What if we want to add lines to a procedure for example if we want to add a diagonal line through the box We d have to tell the turtle to turn and go forward You d better run BOX to get an estimate of the angle and distance remember press BREAK then press R then enter BOX The turtle needs to be turned more than 90 degrees to point along the diagonal Make a guess and return to EDIT mode BREAK E Now place the cursor under the E in END hold down and press the down arrow key This inserts a blank line try the up arrow key to check that END has just been bumped down one line You can now insert your RT and FD commands in this new blank line It will no doubt take you several tries to get the angle and length exactly right that will give you good practice in bouncing back and forth between RUN and EDIT modes No fair using your knowledge of trigonometry with turtles you are supposed to experiment In this chapter we have covered two main topics We have learned how to enter and change multiple command procedures and we have learned how to teach the turtle to understand more complex commands via procedures 21 6 SUBPROCEDURES
76. arts at the beginning of the program area If the END marker is not present then the save stops at the end of the program area After the SAVE operation it is up to the user to again use EDIT mode to remove the START and END markers 162 EDIT MODE You can get into EDIT mode by pressing E when you are in BREAK mode In EDIT mode one can edit the currently loaded modules To start with a blank program area press SHIFT CLEAR in BREAK mode before pressing E The editor is very easy to use It works on the principle that what you see is what you get The first line of text if there is one is displayed on the bottom line To enter lines of text just type them on the screen The cursor will always appear on the bottom line but the text may be moved up or down the screen at will The following keys cause special actions to take place moves the text up one line on the screen or if already on last line then adds a new line to the text end moves the text up one line unless already on the last line moves the text down one line unless already on the first line moves the cursor left one character unless already at the beginning of line moves the cursor right one character unless already at the line end moves to the top line of the text inserts a blank line in front of the current line if the cursor is in column 1 the current line bumps down off the screen if the cursor is not in column 1 then the current line is split i
77. at can be done without much trouble You will minimize distortion if you use a telephoto lens The PRINTSCREEN command tells the computer to make a paper copy of whatever is on the screen The command can be abbreviated as PS The command must be followed by a number or expression with a value between 1 and 4 These numbers tell the computer what printer is in use Pick from the following table 1 RS DMP 110 single width Line Printer 7 2 RS DMP 110 double width 3 RS Color Printer colors 0 magenta 1 yellow 2 violet 3 white 4 RS Color Printer colors 0 blue 1 red 2 green 3 white As with all uses of printers the baud rate must be set correctly See the instructions above 45 PRINTSCREEN command makes of the screen dot dot it does not print letters as units It can take several minutes to print out the whole screen However you can interrupt the process by holding down the key One caution characters printed with the Color Printer are not printed clearly they have colored ghosts In text or list processing operations you may want the results printed at the same time they appear on the screen The ECHO command causes all characters displayed on the screen by PRINT TEXT and REQUEST commands to also be printed If no printer is connected then the characters appear only on the screen ECHO can be turned off with the NOECHO command 11 RECURSION In the Super LOGO language
78. auses execution to pause for the number of tenths of seconds indicated by the expression The expression is evaluated if it is FALSE 0 then the list of statements is skipped If it is TRUE non zero then the list of statements is executed After the list is executed control returns to the WHILE again The expression is then evaluated again The list of state ments is executed repeatedly until the expression is found to be false Puts the screen back in wrap mode TURTLE GRAPHICS AND DISPLAY COMMANDS STATEMENT ABBREVIATION REMARKS BACK expr BK BACKGROUND expr BG BAUD expr CLEAN moves the turtle backward the number of steps denoted by the value of the expression If the tur tle s pen is down then a line of the current pen color is drawn as the turtle moves sets the background color of the screen to color 0 1 2 or 3 The default background color is 3 This sets the serial port baud rate at location 0095 in memory It affects all data sent to the printer This includes program listings from BREAK mode and the PRINTSCREEN com mand The possible values are BAUD RATE VALUE 300 180 600 87 1200 41 2400 18 When the computer is first turned on the BAUD rate is set at 600 baud paints the entire display area the background color without moving the turtle 171 CLEARSCREEN CLEAR CLEARTEXT CT COLORSET expr DOT DRAW ECHO FORWARD expr FD FULLSCREEN FS FULLTEXT FT HIDETURTLE HT
79. be entered in RUN mode they may only be used within a Super LOGO procedure 166 HOW TO EXECUTE A SUPER LOGO PROCEDURE FROM RUN MODE To run a procedure entered via EDIT or DOODLE mode enter the name of the procedure Follow the procedure name with any arguments to be passed to the procedure then press ENTER Each argument is preceded by at least one space An argument can be a number a variable a word a list or an expression If an expression is used it must be enclosed in parentheses You can interrupt execution of a procedure at any time by pressing the BREAK key Pressing any key but BREAK causes execution to resume at the point where it paused pressing BREAK a second time leaves RUN mode and enters BREAK mode DOODLE MODE You can enter DOODLE mode from RUN mode by pressing the key DOODLE mode allows the creation of a turtle graphics procedure that will draw a shape without requiring that the user even know how to read In DOODLE mode the screen displays sign The user enters a word nonsense or otherwise of at least one letter or number and presses ENTER The word is the name of the procedure to be created as a picture 1s drawn Now the numeric keys marked by the special keyboard overlay can be used to enter turtle graphics commands Each time a key is pressed the specified command is executed by the turtle At the same time a procedure is created in the program area This procedure can be viewed in EDI
80. bit more complex example an outline of a plane The dot pattern is X X X X XXXXXXX S XXXXXX XXXXXXX XXXXXXX 89 and the procedure created in DOODLE mode and translated to EDIT mode is TO PLANE SHAPE RRFFFLLFLLFRFR FFFFFFRRFFFFFFF LFLLFLFFFFFFFRRF FLFLLFLFFRRFFFF FFFLFLLFLFFFFFF FRRFFFFFFRFRFLL FLLFF END When we go to more complex shapes we prefer to work with paper rather than with DOODLE mode There are several reasons for this One is that the B command is very useful The other is that we must be very careful if we are to avoid problems when the turtle shape is turned to the 45 degree positions As is our custom we will illustrate with an example We want to use the following stick figure as a turtle shape We must choose our pathway through the figure carefully The problem points are points where lines meet To avoid problems we avoid shortcuts and return to junction points by backtracking exactly The pathway we take is indicated on the second figure The dotted lines indicate backtracking with the pen raised Remember if we did not raise the pen when back tracking then the lines would be complemented a second time that is erased The only place where we don t backtrack is on the head If a closed figure is symmetrical then it will stay closed when rotated 90 other point to note carefully is when to raise lower the dot will be comple mented if the pen
81. c tion denotes the source from which messages are to be received If the argument is 255 then mail is received from any turtle that has sent mail addressed to the current turtle If the argument is not 255 then it denotes the identification of the turtle from which mail is to be received If more than one message is available for delivery then the oldest undelivered message is the one returned If no messages are available then a value of zero is returned returns the identification of the current turtle The main turtle is num ber 0 The others are numbered from 1 to 254 returns a measure of the distance from the current turtle to the one with the specified identification The measure is equal to the number of steps in the X direction plus the number of steps in the Y direction If no turtle exists with the specified identification then the distance to HOME is measured returns a value from 0 to 63 denoting the position of one of the game paddles joysticks The arg is a value from to 3 PADDLE gives the up down of the left paddle PADDLE 1 gives the right left of the left paddle PADDLE 2 gives the up down of the right paddle And PADDLE 3 gives the right left of the right paddle For up down the minimum value is up For right left the minimum value is left returns x y returns INT INT x INT y returns a random number from 0 to arg 1 accepts one character from the keyboard and returns a word consisting of that character
82. cabinet has been opened or if the Equipment or Software has been subjected to improper or abnormal use If a manufacturing defect is discovered during the stated warranty period the defective Equipment must be returned to a Radio Shack Computer Center a Radio Shack retail store a participating Radio Shack franchisee or a participating Radio Shack dealer for repair along with a copy of the sales document or lease agreement The original CUSTOMER S sole and exclusive remedy in the event of a defect is limited to the correction of the defect by repair replacement or refund of the purchase price at RADIO SHACK S election and sole expense RADIO SHACK has no obligation to replace or repair expendable items B RADIO SHACK makes no warranty as to the design capability capacity or suitability for use of the Software except as provided in this paragraph Software is licensed on an 5 15 basis without warranty The original CUSTOMER S exclusive remedy in the event of a Software manufacturing defect is its repair or replacement within thirty 30 calendar days of the date of the Radio Shack sales document received upon license of the Software The defective Software shall be returned to a Radio Shack Computer Center a Radio Shack retail store a participating Radio Shack franchisee or Radio Shack dealer along with the sales document C Except as provided herein no employee agent franchisee dealer or other person is authorized to give any warranti
83. cards is not visible until a hand is completed The dealer has several advantages The dealer wins ties and the dealer plays last thus giving you the opportunity to exceed 21 and lose One other complication is that all face cards have a value 10 and the aces can be counted as either Lor 11 The game as played seriously has a few additional rules which are included to make betting more interesting We won t bother with those here The main procedure BJACK plays the role of the dealer that is it handles the cards and it plays the dealer s hands The first step is to shuffle the cards using DECK BJACK is very long because of the number of non repeating steps but when we follow it through we find that it is pretty simple Following DECK which supplies a shuffled deck a series of MAKE and PRINT commands deal one card face down to the dealer one to the player a second face up to the dealer and a second to the player The cards that are known to the player at this time are printed The procedure CHECK calculates the value of any hand sent to it as a list and returns the value as a number The value of the dealer s hand is kept in D and the value of the player s hand is kept in A value of 21 with just two cards an ace and a face card or a 10 is an auto matic win The sequence IF D 21 PRINT DEALER WINS ELSE IF P 21 PRINT YOU WIN checks for that situation If neither IF condition is true then the procedure be
84. ching The role of the learner is all important Super LOGO puts the student in the role of explorer one who sets goals problems to solve and tries to find a way to those goals The role of the teacher is guide one who stays in the background as much as possible one who does not set the goals for the learner and one who assists only when asked Effective use of Super LOGO has much of the flavor of play It s not whether you win or lose but how you play the game The goal the student reaches is not as important as the process of seeking the goal Super LOGO is based on a set of ideas for use of the computer These ideas were first devel oped under the name LOGO Many people have contributed to the LOGO project too many to list but we must mention the names Wallace Feurzeig Harold Abelson Andrea diSessa and with special emphasis Seymour Papert Most of the development and testing of LOGO was done at MIT There were two vital steps in bringing the LOGO approach to the attention of the educational community One was the publication of two books Mindstorms by Papert and Turtle Geometry by Abelson and diSessa Any serious user of LOGO will want to read those books The other was the implementation of the LOGO language on microcomputers a step which decisively moved LOGO from the laboratory into the classroom If you are already familiar with LOGO you will find much of Super LOGO to be familiar too Wherever possible we have kep
85. ckets square root ST start marker starting Logo stick figure STOP stop marker stopping procedures store subprocedures SUM switch letters SX SY synchronize TEST TEXT text printing text window THING thrust TO top down top level TRACE transform list TREE truth value turtle heading turtle name turtle number turtle shape VANISH variable variable global variable local variable names vertical size U V volume on cassette recorder WAIT WALK WAR WHILE WORD word search words WRAP wrap around X Y proportions XCOR XLOC YCOR YLOC W X Y Z 109 167 113 10 175 42 163 161 90 48 170 42 163 86 41 23 112 180 145 37 175 37 175 93 118 170 170 43 25 166 176 180 102 170 26 26 50 170 126 47 81 48 9 77 77 87 79 171 29 176 30 176 30 176 67 11 41 70 92 136 80 109 180 150 107 175 46 7 11 60 180 85 180 60 180 85 180 RADIO SHACK DIVISION TANDY CORPORATION U S A FORT WORTH TEXAS 76102 CANADA BARRIE ONTARIO L4M 4W5 TANDY CORPORATION AUSTRALIA BELGIUM U K 91 KURRAJONG AVENUE PARC INDUSTRIEL BILSTON ROAD WEDNESBURY MOUNT DRUITT N S W 2770 5140 NANINNE NAMUR WEST MIDLANDS WS10 7JN 7 85 TM Printed in U S A
86. cle from the size of the step it s hard to find the optimum number of steps for the best circle and it s hard to figure where the circle is centered The following procedure is a useful alternative TO ARC X Y RADIUS DEGREE PU SX X SY Y REPEAT DEGREE FD RADIUS DOT BK RADIUS RT 1 END We ve used a new turtle command DOT As you would guess DOT tells the turtle to make a dot on the screen For a circle try ARC 150 100 20 360 ARC 120 120 40 360 For an arc try ARC 60 60 100 100 For a partial circle try ARC 160 90 60 240 38 ARC is slower than CIRCLE but in some situations it is more convenient With some values of RADIUS you might be able to get the same accuracy with fewer steps for example REPEAT 180 and RT 2 but then the number of degrees will have to be divided to get the right number on the REPEAT The following program again makes use of the SX and SY here to get the right relative spac ing of independent parts The correct numbers for the two are found by trial and error Try the procedures with a variety of pen colors and backgrounds Remember to remove the split screen by entering DRAW KIRSTIN in RUN mode TO KIRSTIN CLEAR SX 60 SY 80 REPEAT 18 PENT 20 RT 20 SX 95 SY 82 REPEAT 9 PENT 15 RT 46 END TO PENT SIDE REPEAT 5 FD SIDE LT 72 FD SIDE END 10 SAVING LOADING AND PRINTING YOUR SUPER LOGO PROCEDURES Although Super LOGO procedures can do an amazing amount with ve
87. d s procedure for final comparison so here we use DOODLE mode One task is to ask the child to complete a partially drawn figure but in another position TO PATTERN6 RT 180 SX 70 FD 50 RT 90 FD 20 FD 20 90 FD 10 RT 90 LT 96 FD 10 LT 90 FD 10 10 90 FD 20 RT 90 RT 90 FD 50 RT 90 FD 70 SX 198 SY 96 SH 180 50 RT 90 FD 70 RT 90 END RT 90 FD 10 RT 90 FD 20 FD 50 71 PATTERNG Remember that in entering DOODLE mode it will be necessary to name the procedure that the child is creating The comparison of the two figures can be made nicely Let s assume that the child s procedure is named ZZ After ZZ is completed get into RUN mode do the following RT 180 6 SX 70 SY 146 2 ZZ This will rotate the original figure draw the child s figure over the rotated original in another color The result will be even more satisfying when the child is drawing the whole fig ure in the new position Of course the above set of instructions could be combined into another procedure so as to speed the comparison The DOODLE mode projects can become quite complex For example a long DOODLE mode project could be teaching the turtle to write in handwriting The key is to name each proce dure for drawing a cursive letter with that single letter as the name Thus cursive a should be given the procedure name cursive b the procedure name B etc Then in RUN mode every time a letter is typed f
88. de gets you into EDIT mode prints contents of internal program area on the printer connected to the serial port prints same as P command except that the Q sends a line feed after a return character m allows loading of module into the internal program area After you press L the computer prompts for a module designation with the message LOAD The module is then read from the specified source into the inter nal program area To load from tape enter T prompts for a module designation with the message MERGE It then reads from the specified source and appends the file to the end of the lines currently in the program area MERGE works exactly like LOAD except that the loaded file is added to the end of the current program area s prompts for the module name with the message SAVE then writes the contents of the internal program area to the specified destination To save on tape enter T Normally the entire program area is saved but it is possible to specify that only a portion of the program area be saved To do so use EDIT mode to insert the special START and END markers in the program text The START marker consists of two gt characters such as gt gt inserted just before the first character to be written out The END marker consists of two characters such as lt lt just after the last character to be written Either or both markers may be present If the START marker is not present then the save st
89. dle of the screen X 128 Y 96 The turtle heading at home is zero degrees or straight up The screen dimen sion in the X direction across the screen goes from 0 at the left edge to 255 at the right edge The screen dimension in the Y direction up and down goes from at the bottom to 191 at the top The lower left hand corner of the screen has coordinates 0 0 The upper right corner has coordinates 255 191 The screen is normally a wrap around space that is if the turtle runs off the top of the screen it reappears on the bottom If it runs off the left it reappears on the right etc In that sense the plane on which the turtle walks is infinite in any direction The turtle may be pointed in any direction from 0 to 359 degrees Straight up is 0 degrees and the direction increases as the turtle rotates to the right or in a clockwise direction SPLIT SCREEN When you get into RUN mode the screen is divided into a graphics area and a text area The text area is the bottom three lines of the screen The graphics area is the rest of the screen In split screen mode neither the turtle nor any lines drawn by the turtle appear in the text area If the turtle is moved into this area it becomes invisible until moved back into the graphics area The user can use the FULLSCREEN or DRAW command to change from split screen mode to full screen mode In full screen mode text lines still use the bottom lines of the screen but the turtle and lines drawn a
90. dure counts the number of words in a list TO LENGTH LIST COUNT MAKE COUNT WHILE LIST lt gt MAKE COUNT COUNT 1 MAKE LIST BL LIST OUTPUT COUNT END The WHILE segment removes words from the list and increments the count until the list is empty an empty list is indicated by the symbols LENGTH can be combined with PICK to select a random word from a list TO PICKRANDOM L X LENGTH L PICK 1 RANDOM RESULT L OUTPUT RESULT END For example FT PICKRANDOM A B C D E F G H PRINT RESULT H When we call LENGTH we only pass it the list but LENGTH expects two variables Remem ber that omitted variables are assumed to be zero LENGTH returns a result which is subse quently used as the argument for RANDOM result does not have to be picked up at once it stays available until it is picked up or until it is overwritten by another OUTPUT from another subprocedure called by this procedure 124 next procedure tests to see if an item is member of a list we just output of the words TRUE or FALSE to indicate the result Instead we could count and output the position of the word in the list or zero if it isn t there TO MEMBER WORD LIST WHILE LIST lt gt IF WORD FIRST LIST OUTPUT TRUE MAKE LIST BF LIST OUTPUT FALSE END To test this enter FT MEMBER IN AT ON IN TO BY PRINT RESULT TRUE Enter other words and lists to check
91. e LT 30 30 and then press ENTER to see the invisible turtle s track Notice that we can type more than a single turtle command on a line as long as we have at least one space between the commands To make the turtle visible again type SHOWTURTLE you guessed it abbreviated ST Then to turn it away from the track type LT 126 At this point the only thing between us and an endless variety of stunning graphics is an immense amount of typing In the next two chapters we ll learn some things which will save us from this immense amount of typing 10 3 REPEAT There many times when we want to repeat series of turtle commands several times For example if we wanted to draw a square we would need to repeat the sequence FD 60 RT 90 four times Fortunately the turtle understands a control statement which saves us from typing the same thing four times in succession The control statement is REPEAT With a clear screen try REPEAT 4 FD 60 RT 990 RFPEAT CFD 60 RT 90 Notice that after the statement REPEAT we must tell the turtle how many times to repeat and we must tell the turtle what to repeat The what is enclosed in parentheses Here the number of times to repeat is 4 and the what to repeat is FD 60 RT 90 The figure the turtle has just drawn may be more of a rectangle than a square On some TV sets the size of a turtle step in the vertical direction is a little different f
92. e version by reducing the number of times the turtle has to be drawn Simply insert a HT command as the first command in the procedure One other change converts the tree into full blossom Try TO TREE2 S IF 0 CLEAR DRAW SY 0 IF 5 gt 6 FD S LT 30 HATCH 1 TREE2 3 5 4 RT 60 HATCH 2 TREE2 3 S 4 VANISH ELSE REPEAT 500 END The addition is the ELSE statement The ELSE is a partner of the IF statement The combi nation says if the current value of S is greater than 6 then obey the commands in the follow ing set of parentheses from FD S through VANISH but if S is not greater than 6 then obey the commands in the parentheses following ELSE The commands following ELSE sim ply delay the completion of the procedure so that we can see the tree with a turtle at the end of each branch Trees are so easy to draw with multiple turtles that we may as well draw a complete forest In fact we ll look at two forests one a deciduous forest in winter and the other an evergreen for est in whatever season you like TO FIR1 N X Y HT SX X SY Y PC 0 BK N 2 RT 90 FD N 4 LT 90 FD 6 N 2 RT 90 FIRT1 N X END TO FIR11 N X PC 1 RT 15 FD N LT 129 FD 3 N WHILE XLOC ME X FD 2 END TO FIR2 N X Y HT SX X SY Y PC 0 BK N 2 LT 90 FD N 4 RT 90 FD 6 N 2 LT 90 FIR22 N X END 83 FIR22 N X PC 1 LT 15 FD N RT 129 FD 3 WHILE XLOC ME lt X FD 2 END TO FIR N X Y T HT HATCH T FIR1
93. e addition of list processing and decimal arithmetic practical and the feedback showed us many small improvements which make the package more useful Our debt to the original designers of the LOGO language is acknowledged in Chapter 1 We would also like to thank our children Aaron Jenell and Kirstin whose responses to early ver sions of Color LOGO convinced us that we were on the right track George Gerhold Larry Kheriaty Table of Contents ntrodifetion M T 1 1 A Bit About Color 3 2 Startad sce n u end Coco SSS auos sh seio c cou 5 11 j Modes Editing ss 15 9 Proced ures eene 19 6 SuDprOCedufes 23 EE ssp s 29 8 Colors us amupa 33 9 Other Turtle Command s 37 10 Saving Loading and Printing Procedures 41 Ji RECUS TON n E s SA ss 45 12 DOODLE Mode Procedures Without Typing 55 13 One Key u uuu 59 14 Use of DOODLE Mode and Set 63 15 Additional Editing Features 75 TIO Multiple Turtles i iaaea iii SE DASE s su tua a
94. e computer s memory we have taught the turtle to understand a new word The turtle now understands RECTANGLE in the same way that it understands LEFT RIGHT FORWARD and BACK Before moving on to other procedures we want to review use of the editor Press to return to BREAK mode then press E to reenter EDIT mode The screen should now show the first line of the procedure RECTANGLE Let s change the name to BOX Use the right arrow key to position the cursor under the R in RECTANGLE Then type BOX Remember overtyping replaces characters We need to delete the remaining letters which we do by hold ing down the key and pressing the left arrow key We can see the rest of the lines in the procedure by pressing either or the up arrow key several times 20 It is good programming practice to clarify the structure of a procedure indentation we want the procedure BOX to look like this TO BOX FD 50 RT 90 FD 30 RT 90 FD 50 RT 90 FD 30 END To make these changes we must insert a couple of spaces at the beginnings of the second and third lines Move the second line to the bottom of the screen by using the up and down arrow keys The cursor will move to the start of the line whenever you change lines To insert spaces hold down the key and press the right arrow key If this does not insert spaces it means that the line is already full Insert spaces at the start of line 3 as well The structure of the procedure would be even cle
95. e list This pen should not be confused with the turtle pen that draws when a FORWARD or BACK turtle graphics statement is executed D put the turtle shape pen down if the pen was previously up then putting it down will cause the current pixel to be complemented MULTIPLE TURTLES Normally one turtle exists The user can create additional turtles by using the HATCH state ment Each turtle then runs its procedures independently of the other turtles The HATCH statement assigns an identification number to each turtle That number may be used by other turtles to send mail or request location information about the turtle The main turtle is always number 0 Other turtles can have a number from 1 to 254 When a turtle other than the main one exits from the procedure given it when it was HATCHed it goes out of existence leaving behind only the lines it drew on the screen The VANISH statement also causes the turtle to go out of existence The main turtle in contrast can only go out of existence by executing a VANISH statement 181 If the main turtle exits from the procedure given to it from RUN mode it will return to RUN mode where the user can then enter its next command or procedure to run If when the main turtle is in RUN mode there are other turtles then the other turtles cease to move Each time the key is pressed each of the turtles executes one program statement This has the effect of stepping the hatched turtles along at a controlled
96. e probably tired of following the manual consumed with curiosity What will happen if I change the number on the REPEAT in MANY what will happen if I change the angle in MANY what will happen if I restore the commands to draw the diagonal in BOX Don t hesitate to find out by trying that s the whole point of Super LOGO Try triangles pen tagons hexagons threes and fives instead of just boxes and fours Here is another sample TO DIAMOND FD 50 LT 45 FD 50 LT 135 FD 50 45 FD 50 END TO DIAMOND2 REPEAT 29 DIAMOND RT 40 END 24 When you run DIAMOND2 the pattern the screen is missing the bottom portion That is because the computer is using split screen the top of the screen is reserved for graphics and the bottom four lines are reserved for text The turtle draws behind the text portion of the screen 1t does not wrap around until it reaches the very bottom of the whole screen However when the computer is using a split screen we cannot see what the turtle draws behind the text area We can see what the turtle draws on the full screen by entering one of the statements DRAW or FULLSCREEN abbreviated FS before entering the procedure name Of course this can all be on one line for example DRAW DIAMOND2 Be careful of one thing when using the full screen If you type more than three lines of com mands in RUN mode the text lines at the bottom of the screen will scroll up In full screen the
97. e two combinations the original word and the word with two letters switched TO 2 WORD PRINT WORD SW WORD 1 2 PRINT RESULT END 145 We think of PERM2 as giving the combinations generated by switching letter two with itself that is no change and by switching letter 2 with letter 1 Some examples to try FT PERM2 GO FT PERM2 AT Three letter words are generated by switching letter 3 with itself and calling PERM2 then by switching letter 3 with letter 2 and calling PERM2 and finally by switching letter 3 with letter 1 and calling PERM 2 TO PERM3 WORD NEW N MAKE NEW WORD MAKE N 3 REPEAT 3 IF N 3 SW NEW N 3 MAKE NEW RESULT PERM2 NEW MAKE NEW WORD MAKE N 1 END You might check this with a three letter word to see that 1t generates all the combinations of the letters For example FT PERM3 CAT Four letter combinations are generated by switching letter 4 with itself with letter 3 with letter 2 and with letter 1 and in each case calling PERM3 after the switch TO PERM4 WORD NEW N MAKE NEW WORD MAKE N 4 REPEAT 4 IF N lt 4 SW NEW N 4 MAKE NEW RESULT PERM3 NEW MAKE NEW WORD MAKE N N 1 END We can now write the recursive general version by comparing PERM3 and PERM4 There are several places where the number 3 appears m PERM3 the number 4 appears the equivalent positions in PERM4 We simply replace those numbers w
98. ediately Now we want a way to tell the computer to wait until it receives appropriate information from the keyboard The READCHAR function abbreviated RC accepts a single character from the keyboard This character becomes a word The character does not appear on the screen when the key is pressed we must print it if we want it to appear We ll begin with a very simple example a procedure which asks whether a statement is true or false TO QUES PRINT COWS CAN FLY PRINT TYPE FOR TRUE PRINT TYPE F FOR FALSE IF RC PRINT RIGHT ELSE PRINT WRONG END This procedure starts by printing three lists which give the statement and the instructions The RC READCHAR function waits until a key is pressed and makes the key pressed into a word If that word is the same as the word F F that is if the key was pressed then the command is to print the word RIGHT otherwise print the word WRONG When you enter and run QUES remember FT QUES you will notice that the letter selected does not appear on the screen If we want to show the letter then we must print it There are several ways this can be done TO QUES1 FT PRINT COWS CAN FLY PRINT TYPE T FOR TRUE PRINT TYPE F FOR FALSE IF RC F PRINT SE F RIGHT ELSE PRINT SE T WRONG END TO QUES2 ANSWER FT PRINT COWS CAN FLY PRINT TYPE T FOR TRUE PRINT TYPE F FOR FALSE MAKE ANSWER RC PRINT ANSWER IF ANSWER F PRINT RIGHT IF
99. edictable However as we become more serious we often will have a problem we wish to solve Then we should work from the top level down Now we illustrate that process The sample problem is to create the following pattern PATTERN Obviously the figure is so symmetrical that it must contain a repeated pattern Counting shows that something is repeated six times The crucial step is to recognize that the element that is repeated six times is a square with a circle inside PATI Therefore our main procedure could be TO PATTERN REPEAT 6 SQUARE CIRCLE RT 60 END 26 six fold symmetry tells us to repeat 6 times with turns of 60 because 6 60 360 As yet we have no idea how to draw a square with a circle inside Notice that we use the hyphen as part of the procedure name to avoid using a space a space between the two words would indicate two subprocedures We can use a hyphen this way any place it cannot be con fused with a minus sign Now we move to the next lower level TO SQUARE CIRCLE CIRCLE SQUARE END Again we break the task into simpler tasks This time the breakdown is obvious you draw a square around a circle by drawing a circle and then a square Now we drop down to level 2 The obvious procedure for drawing a circle is TO CIRCLE REPEAT 360 FD 1 RT 1 END This gives a circle but one that is rather large If you try it you ll see that we ll never get six of those on the screen To m
100. er of tenths of a second here it waits 3 seconds each time Be sure that the child s procedure is named F so that there is simple correspondence between the name and the drawing If you still have the Set in memory you ll have to delete F from that set Once the child is familiar with the shape of the letter or of several letters you can let the child try making letters by connecting dots Here the procedure must draw the dots preferably starting at the home position To run the procedure DOTM you ll need to have the BIGDOT procedure from Chapter 13 in program memory TO DOTM CLEAR BIGDOT FD 60 BIGDOT RT 135 FD 30 LT 45 BIGDOT LT 45 FD 30 RT 45 BIGDOT RT 96 FD 66 BIGDOT HOME END 70 this procedure we ve been careful to always the turtle pointing the horizontal direc tion to keep the spacing of the dots perfectly regular That may not be essential This dot to dot exercise works best for those letters and numbers where the pen never need be raised Most letters require that the pen be raised The dot pattern for these may be a bit of a puzzle perhaps a worthwhile challenge If that is too difficult color coding the dots into two or three sets or adding intermediate dots may help The ability to visualize how things will look in other positions is worth developing The idea here is to give a figure in one position and to ask the child to doodle it in another position We are going to reuse the chil
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102. es of turtle moves called procedures e doodle mode lets children who are too young to read or type use the program e A SLOW command lets you control how fast the turtle moves e Screen colors be changed Animation is possible with Super LOGO Variables and arithmetic expressions can be used in the sets of turtle moves that you write and save e Multiple turtles can work in concert on graphics and on list processing tasks Super LOGO is a language for beginners For this reason the Super LOGO manual has been written to guide you through use of the language step by step with many examples and illus trations Here is a summary of the organization of the manual 1 Chapters 1 through 11 introduce turtle graphics the LOGO syntax and use of the editor Readers who are already familiar with LOGO may wish to skim these chapters or to bypass them in favor of the summary in Appendix I 2 Chapters 12 through 18 cover features unique to Super LOGO a Chapters 12 through 14 provide hints for using Super LOGO with very young children b Chapter 15 provides more information about using the Super LOGO editor c Chapters 16 through 18 introduce the use of multiple turtles and new turtle shapes 3 Chapters 19 through 26 cover list processing including multi tasking applications of list processing 4 Chapter 27 contains sample sets of more complex turtle moves that you may wish to explore The Radio Shack Supe
103. ess the key twice once to interrupt the procedure and a second time to get into BREAK mode 2 The RESET button located on the right rear side of the computer will always return you to BREAK mode but you will lose all programs memory 3 A complete restart as described on page 5 will place you in BREAK mode BREAK mode will be covered in detail in Chapters 3 and 10 For now let s move into RUN mode by pressing R There is the turtle sitting in the center of the screen facing straight up Admittedly this turtle does not bear a strong resemblance to the ordinary pond type tur tle but like an ordinary turtle it can crawl forwards and backwards and it can turn right and left Unlike ordinary turtles computerized turtles can drag their tails to leave tracks in colors or raise their tails and not leave tracks Turtles can even be made invisible The name turtle was given originally to a tiny mechanical robot which could be made to crawl around the floor under computer control The name probably had much more to do with the speed of the robot than with the shape of the robot The track left by the turtle was called a turtle graphic The term turtle graphics is now used to indicate a way of drawing where lines are described by a direction and a length the alternative is to describe a line by giving the coordinates of the two end points of the line a method called strangely vector graphics The item which moves is c
104. gain If a number and a question mark appear after the then the procedures were not saved properly so try again Loading programs from cassette is also simple Again it is necessary to be in BREAK mode In response to the BREAK mode prompt press L The prompt then will read LOGO LOAD The response here is exactly the same as for SAVE Use the letter T to load from tape Then press ENTER to start the process Of course you will have to have the volume on the cassette recorder set to about 5 have the tape rewound and have the PLAY button depressed before pressing ENTER 41 At times you will want to carry out some more elaborate transfers between the computer memory and tape For example you might want to add some procedures already on tape to the procedures in memory This would be the case if you had created a module of procedures for drawing circles and polygons which you planned to use in many projects module of proce dures can be added to whatever is already in memory by use of the MERGE operation Simply respond to the LOGO prompt with M At this point the prompt will be LOGO MERGE __ To start the process enter T We just learned how to combine sets of procedures how do we save only a portion of what is in memory The computer recognizes special start and end markers If these markers are present in a set of procedures then a SAVE operation saves only the lines between the two markers Therefore to
105. gins executing the commands under the ELSE which follows the above three lines If either of the IF condi tions is true the hand is over and a new hand is begun the outermost WHILE L p Next the player plays his or her hand Cards can be drawn until the value of the hand is over 21 The player is asked to respond with a Y if they want another card If they do a card is dealt off the top of the deck the new hand is printed and a new value of the hand is obtained from CHECK 140 L DEAL PLAY D P C FT DECK MAKE L RESULT WHILE L lt gt MAKE DEAL FIRST L MAKE L BF L MAKE PLAY FIRST L MAKE L BF L MAKE DEAL SE DEAL FIRST L MAKE L BF L PRINT DEALER SHOWS PRINT BF DEAL MAKE PLAY SE PLAY FIRST L MAKE L BF L PRINT YOU HAVE PRINT PLAY CHECK DEAL MAKE D RESULT CHECK PLAY MAKE P RESULT IF D 21 PRINT DEALER WINS ELSE IF P 21 PRINT YOU WIN ELSE MAKE Y WHILE lt 22 amp C Y PRINT CARD MAKE C RC IF C Y MAKE PLAY SE PLAY FIRST L MAKE L BF L PRINT PLAY CHECK PLAY MAKE P RESULT IF P gt 21 PRINT DEALER WINS ELSE WHILE D lt 17 MAKE DEAL SE DEAL FIRST L MAKE L BF L PRINT SE DEALER DEAL CHECK DEAL MAKE D RESULT IF D P amp D 22 PRINT DEALER WINS ELSE PRINT YOU WIN PRINT NEXT HAND END 141 actions pr
106. gle wide or Line Printer 7 2 RS DMP 110 double wide 3 RS Color Printer with colors 0 1 yellow 2 blue 3 black 4 RS Color Printer with colors 0 green purple 2 orange 3 white On the Color Printer characters displayed on the screen are not clearly drawn on paper but have colored ghosts The appropriate baud rate must first have been set either by the BAUD com mand or by setting location 0095 prior to running LOGO Since PRINTSCREEN can take several minutes to complete you can cancel it by holding down the key while the printer is printing If the printer is not ready when this command is issued the command is ignored turns the turtle right clockwise the specified number of degrees points the turtle in the direction specified by the expression The heading can be from to 359 degrees 0 degrees is straight up sets pen state up 0 or down lt gt 0 and pen color SETX expr SX moves the turtle by changing its X coordinate to the value specified No line is drawn The value may be from 0 left edge to 255 right edge SETY expr SY moves the turtle by changing the Y coordinate to the value specified No line is drawn The value may be from 0 bottom to 191 top SHAPE shape list changes the shape of the current turtle to a shape denoted by the shape list See TURTLE SHAPE LIST below SHOWTURTLE ST makes the turtle visible EXPRESSIONS The expr designation above denotes
107. h out turning the turtle At some point the child will need practice in learning letters and numbers Part of learning to recognize them is to look at them very carefully and this can be encouraged by use of DOO DLE mode activities The child will probably want to use the letters later to write simple words so we ll save the procedures they make The first tasks could be simply copying from a model Because most people identify computers with mathematics here we ll counter that ten dency by using letters for examples Well begin with the letter F We need a procedure to draw the model TO DRAWF CLEAR SX 50 SY 146 RT 180 FD 50 SX 50 SY 146 LT 90 FD 30 SX 50 SY 126 FD 20 HOME END This will draw a large capital F as you can see by running the procedure However it will draw the F so quickly that it gives the child no hint as to the order in which the lines should be drawn The order can be indicated in several ways Color can be used draw the red part then draw the blue part We can put delays between the strokes to make the sequence on the example visible We ll use both techniques 69 DRAWF CLEAR SX 50 SY 146 RT 180 PC 1 FD 50 WAIT 30 SX 50 SY 146 LT 90 PC 2 FD 30 WAIT 30 SX 50 SY 126 FD 20 WAIT 30 HOME END Note The DRAWF procedure could not be called DRAW F because LOGO command words such as DRAW cannot be used as part of a hyphenated procedure name The command WAIT does nothing but wait the indicated numb
108. hat same shape At one addi tional level of detail that gives Each of the lines in this drawing is turn made up of four lines with the basic shape etc This is a place to use recursion TO FRACTAL N IF N lt 15 FD N STOP FRACTAL N 3 LT 60 FRACTAL 3 RT 120 FRACTAL N 3 LT 66 FRACTAL N 3 END Running FRACTAL 50 will show the pattern You may want to enter DRAW RT 90 SX 0 FRACTAL 50 to turn it the way we ve shown it in the manual Notice that the pattern divides the whole length into thirds that is why we divide by 3 on the recursive calls However the resulting length will change somewhat depending on the conditional IF statement because of the round off loss in arithmetic You ll see that if you change the conditional to something finer such as N lt 4 That pattern looks like the edge of a snowflake Why not make it into something six sided ol FLAKE N CLEAR REPEAT 6 FRACTAL N RT 60 END You may have to play with the starting position SX and SY and the size to get a nice figure without wrap around You may also prefer the figure you get when FLAKE is made to draw three sides at 120 degrees Other variations are possible We can replace FD N in the IF statement with a more elaborate series of commands A few examples follow TO FLAKE N CLEAR SX 50 SY 46 REPEAT 3 FRACTAL N RT 126 END Replace the conditional statement in FRACTAL with IF N lt 9
109. he cursor where you want the break to occur then press SHIFT down arrow to break the line You ll have to insert some spaces to move the name over as shown above This we think 16 the final form of the note so we exit mode press To make a last check we get back into EDIT mode press get the whole note on the screen without repeated pressing of up arrow or we press up arrow twice This will show us everything in memory If we want to interrupt this process Just press any key to stop the scan To restart the scan press up arrow twice again To jump back to the start of the text press the key That covers the basics of using the editor You should practice a bit with it so that when we return to Super LOGO you can concentrate on the language and not have to worry about the mechanics of the editor Chapter 15 covers the more advanced features of the editor To conclude this chapter we give a summary of the editing features Press get into EDIT mode BREAK E display the next line of text has effect at last line add a line at end ENTER then type the line of text move text down one line no effect at top line move cursor right no effect at line end move cursor left no effect at line start replace character insert character delete character or delete blank line insert line break line return to top line scroll or scan through text stop scroll o
110. he game The four tasks turtles are going to have to communicate using the SEND command and the MAIL function Only numbers can be sent and received so some codes for the face cards which are words like and K must be established Because the highest number card has the value 10 we will assign the Jack 11 the Queen 12 the King 13 and the Ace 14 The subprocedure NUMBERTOCARD converts the numbers 11 to 14 to the appropriate card symbol The sequence WHILE C1 0 C1 1 waits until player one sends a message plays a card The message will be the numerical value of or assigned to the card The procedure then uses a similar set of commands to wait for a second card Then the two cards are converted back to symbols by NUMBERTOCARD and the symbols are printed out This is useful for us when we are checking the procedures but it is not essential for the game Finally the values of the two cards are compared and appropriate messages are sent The value 15 indicates that the player lost that card a value between 2 and 14 indicates the card that was won The procedure as written gives player 1 an unfair advantage player 1 wins all ties If player 1 is originally dealt an ace then player 1 can never lose Well live with that limitation here but you might want to change the proce dure to correspond to your local version of the game Finally the values of C1 and C2 are reset so that WAR will wait for cards from the playe
111. her the S key was depressed If the S key was depressed then the statement SEND is run The SEND statement sends a message to another turtle by leaving the message in a mailbox The first number after the SEND is the address of the message In the line we are analyzing the address is 2 so this message can be picked up from the mailbox only by turtle 2 The address can be an expression as well as a number The second number after the SEND is the message Here the message is the number 1 in general the message can be any number in the range covered by Super LOGO 32768 to 32767 or an expression which gives a number in this range To review SEND 2 1 leaves the message 1 in the mailbox for turtle 2 Because the S key is to move the runner turtle 2 the message 1 must mean move We ll see that in the procedure RUNNER Although we aren t going to use it in this example there is a way to send a general message to the first turtle that picks up its mail We just use the turtle address 255 then the next turtle that inquires will get the message If we wanted to send an all points bulletin to all turtles we could do so by setting a global variable see Chapter 8 The rest of GETKEYS is just more of the same We check for each of the keys which control the runner and send a message to turtle 2 if one of them is depressed and we do the same for the three keys which control turtle 3 Notice that the WHILE 1 1 causes turtle 1 to continue to
112. here there is sufficient strategy that the player must think while playing Our first sample game is called CATCHEM There are two players or one two handed player who manipulate objects on the screen by pressing keys on the keyboard The object is for the chaser to catch the runner When the chaser catches the runner the scorekeeper changes the score and a new chase starts There is an advantage to using multiple turtles here as we can assign each turtle one task This simplifies the programming greatly for example we do not have to move a cursor to the scoreboard to change the score and then return to make the next move The master procedure simply names the procedures and assigns the four tasks to four turtles We use turtle 0 and three others TO CATCHEM CLEAR DRAW HATCH 1 GETKEYS HATCH 2 RUNNER 20 HATCH 3 CHASER SCOREKEEPER 0 END The names of the procedures are pretty descriptive RUNNER controls the runner and CHASER controls the chaser SCOREKEEPER keeps the score GETKEYS reads input from the keyboard Of course the various turtles need to communicate and that is the main new idea we will illustrate in this example 97 Let s with the keyboard TO GETKEYS X HT WHILE 1 1 MAKE X KEY IF X S SEND 2 1 IF X D SEND 2 45 IF X A SEND 2 315 IF X K SEND 3 1 IF X 4 SEND 3 45 IF X J SEND 3 315 END First we see a trick we used before the use of WHILE 1 1 as an effecti
113. his or her hand and the high card takes both cards played Captured and played cards are placed at the end of the winner s hand The point is to capture all the cards a process which is usually very time consuming However the lack of strategy makes the game a good one to start with We choose to make the game a four turtle task because it is list processing the turtles will never appear on the screen The master turtle will deal the cards and handle the rules That is the master turtle will compare the cards played and award the cards to the winner at each step The main procedure is as follows TO WAR L J C1 C2 OVER FT DECK MAKE L RESULT MAKE J REPEAT 26 MAKE J SE J LAST L MAKE L BL L HATCH 1 PLAYER L 26 HATCH 2 PLAYER J 26 HATCH 3 ENDER WHILE OVER 0 WHILE C1 0 MAKE C1 MAIL 1 WHILE C2 0 MAKE C2 MAIL 2 NUMBERTOCARD 1 PRINT RESULT PRINT CHAR 32 NUMBERTOCARD C2 PRINT RESULT MAKE RC IF C1 gt C2 SEND 1 C2 SEND 2 15 IF C2 gt SEND 1 15 SEND 2 C1 MAKE 1 0 MAKE C2 0 MAKE OVER MAIL 3 END 136 This main procedure first sets the screen display calls for a shuffled deck DECK The REPEAT divides the shuffled deck into two hands by transferring the last 26 cards to the list J Then the two players are hatched using the PLAYER procedure not yet written and are given their cards The remainder of the procedure implements the rules of t
114. is down when we move into the dot or if the pen is lowered while we are in the dot Notice that this means that if we draw a line and then cross that line with the pen down the crossing dot will be erased Following the pathway indicated gives the following procedure stated earlier we work this out on paper and enter it directly in EDIT mode so that we can use the B command TO ONE SHAPE LLULLFFFFDFFRRRFFFFFF RRFFFFFFLLFFUBBLLFFFFFFRFD FFFFFFFFRRFFFFLFFUBBRBBBB RFDFFFLLFFUBBLLFFFFRFD FFLFRFFRFRFFRFRFFRFRF END Try this out by running ONE Try rotating it to other positions Notice that when you turn it far enough it is upside down You may not want turtles that do strange things like that for some purposes You can sometimes avoid it if it is a problem by shifting your point of view For example you might decide that it would be nice to have a turtle which actually looked like a turtle If you draw a side view of the turtle then it will look strange with headings like 180 degrees But if you draw a top view of the turtle then it looks fine in any orientation The reason that we drew the stick figure is that we want to show you how to use Super LOGO to do some very simple animation We want to have a figure that will walk We ll need another position for the stick figure so we define another turtle shape The process is the same as before 91 Translating the indicated path into procedure gives TO TWO SHAP
115. ith a variable X 146 PERM WORD X NEW N MAKE NEW WORD MAKE N X REPEAT X IF N lt X SW NEW N X MAKE NEW RESULT IF X 3 PERM2 NEW ELSE PERM NEW 1 MAKE NEW WORD MAKE N 1 END We chose to keep the PERM2 as a special case for further applications so the recursive call is controlled by the IF ELSE combination The new variable X is put early in the list of variables to reduce the variable list on the call NEW and N are just local variables which do not need to be given a value on the call To use this we must give it a word and the length of the word The length can be obtained by a procedure TO START WORD N NEW FT SIZE WORD MAKE RESULT PERM WORD N NEW END TO SIZE WORD COUNT WHILE WORD lt gt MAKE COUNT COUNT 1 MAKE WORD BL WORD OUTPUT COUNT END This is now a complete set of procedures which will print out every combination of letters word you give it When you try it out remember that the number of combinations becomes large very fast There 120 combinations of 5 letters 720 combinations of 6 letters 5040 combinations of 7 letters etc Now you may wonder what we could do with these procedures One possibility is to make a prompter for Scrabble If you give it the letters you have it will generate every possible combi nation You might want to modify PERM2 so that it prints only those combinations which have par
116. itive we write a subproce dure which carries out the operation and which we can use like a new primitive For instance in Chapter 5 we wrote the subprocedure BOX and then we used the word BOX just as we used the primitive operations FD and RT But how do we write subprocedures which supply new functions which produce results and which can be used in other procedures just as we use supplied functions like RANDOM 111 We ll illustrate the process by writing subprocedure which duplicates the action of exist ing function ABS The ABS function returns the absolute value of the argument That is if the argument is positive then no change is made but if the argument is negative its sign is changed The following procedure carries out exactly those actions TO ABSOLUTEVALUE NUMBER IF NUMBER lt 0 MAKE NUMBER NUMBER lt 1 END This procedure does the conversion to a positive number but in its present form it cannot be used as a new function The problem is that the subprocedure ABSOLUTEVALUE does not return the value to the higher level once it has made it positive The command to return a value is the OUTPUT command We can make the subprocedure operate as a function by adding an OUTPUT command at the end TO ABSOLUTEVALUE NUMBER IF NUMBER lt 0 MAKE NUMBER NUMBER 1 OUTPUT NUMBER END On the receiving end the higher level procedure the computer must be instructed to pick up the result For exa
117. lay The first line of commands loads a word which is the player s number into the variable ME The major portion of the procedure is a loop which repeats until the player is out of cards WHILE L lt gt p The variable COUNT keeps track of the number of cards This could also be done by use of the LENGTH subprocedure on L but this way is much faster COUNT is converted into a word so that it can be combined into a sentence like 2 HAS 24 The three lines MAKE FIRST L CARDTONUMBER N 0 SEND 0 RESULT 138 take the next card off the top of the hand convert the card into number A 14 etc and send the card to turtle 0 The next three lines make the player wait for turtle 0 to tell them whether the card won another one or lost The message 15 means that the card was lost so the card is removed from the list L and the COUNT is decreased by 1 Any other message is the numeric code for the card that was won that case the COUNT is increased by 1 the numeric code is translated back to a card and the card played and the card won are moved to the bottom of the hand the list L This process continues unless the list is empty If the list is empty and those of you who have ever played War know how unusual it is to ever finish a game then a message 15 sent to turtle 3 ENDER waits for a game ending message prints an appropriate message on the screen and lets turtle 0 know that it is all over WAR uses seve
118. ly for backup or archival purposes or if additional copies are required in the operation of one computer with the Software but only to the extent the Software allows a backup copy to be made However for TRSDOS Software CUSTOMER is permitted to make a limited number of additional copies for CUSTOMER S own use F CUSTOMER may resell or distribute unmodified copies of the Software provided CUSTOMER has purchased one copy of the Software for each one sold or distributed The provisions of this Software License shall also be applicable to third parties receiving copies of the Software from CUSTOMER G All copyright notices shall be retained on all copies of the Software APPLICABILITY OF WARRANTY A The terms and conditions of this Warranty are applicable as between RADIO SHACK and CUSTOMER to either a sale of the Equipment and or Software License to CUSTOMER or to a transaction whereby Radio Shack sells or conveys such Equipment to a third party for lease to CUSTOMER B The limitations of liability and Warranty provisions herein shall inure to the benefit of RADIO SHACK the author owner and or licensor of the Software and any manufacturer of the Equipment sold by Radio Shack STATE LAW RIGHTS The warranties granted herein give the original CUSTOMER specific legal rights and the original CUSTOMER may nave other rights which vary from state to state 12 84 Radio Shack Super LOGO By Larry Kheriaty and George Gerhold
119. m a list of six TO THROW N CHOICE MAKE CHOICE 1 2 3 4 5 6 PICKRANDOM CHOICE 6 OUTPUT RESULT END THROW uses the subprocedure PICKRANDOM and its subprocedures PICK and LENGTH to do the actual random selection we ve seen PICK PICKRANDOM and LENGTH in Chapter 22 149 DIFFERENCE is new subprocedure which might be useful a variety of projects TO DIFFERENCE OUT LONG WHILE OUT lt gt REMOVE FIRST OUT LONG MAKE OUT BF OUT MAKE LONG RESULT OUTPUT LONG END The procedure works its way through the list of words to be eliminated REMOVE must take a word and a list and remove the word from the list The shortened list is returned as the result and the processed word is peeled off the list in OUT TO REMOVE WORD LIST N LENGTH LIST MAKE N RESULT REPEAT N IF WORD FIRST LIST OUTPUT BF LIST ELSE MAKE LIST SE BF LIST FIRST LIST PRINT SE WORD NOT IN LIST OUTPUT LIST END The critical part of REMOVE is the loop The word in WORD is compared with the first word in LIST If they are the same the shortened list is output If they are not the same then the words in the list are rotated to make another one first If the list is rotated completely without the procedure being completed with an OUTPUT command then the word is not in the list A message indicating that fact is printed and LIST is returned unchanged When you try this set of procedures remember that the
120. m is a map of the modes in Super LOGO BREAK ce The keys which trigger the jumps between modes indicated on the arrows You ve already been in BREAK mode that s the mode that you are in when you start You ve already been in RUN mode you got there from BREAK mode by pressing R Now we want to move into EDIT mode The map shows us that we need to leave RUN mode by pressing the key and then get into EDIT mode by pressing the E key EDIT mode provides a line oriented editor EDIT mode is used to create and alter programs written in Super LOGO but for the rest of this chapter we will forget LOGO and concentrate on the mechanics of using EDIT mode We ll do something familiar write a note to Grandma When you get into EDIT mode a short horizontal line appears at the start of the bottom line of the screen This line is called the cursor The cursor indicates where any typed letters num bers etc will appear Start the note by typing DEAR GRANDMA Press ENTER and the cursor moves to the start of the next line Type the next line as M STARTING TO USE AN EDITOR Again press ENTER to complete the line Notice that this editor produces only upper case letters Super LOGO uses only upper case letters We could continue to enter as many lines as we wanted in the same fashion Let s assume that this is to be a very short note and that we now want to quit editing Press Upon reflecti
121. mi lar to ones which appear in most LOGO books does it recursively TO PICK1 N L IF N 1 OUTPUT FIRST L N 1 BF L OUTPUT RESULT END The approach is to remove words from the front of the list until word N is reached and then to output that word Notice that the OUTPUT function stops a procedure and returns to the next level up To test this procedure enter FT PICK1 3 A B C D EF GHI PRINT RESULT and try it with other numbers and lists While PICK1 works it is very wasteful of memory The reason is that the computer makes another copy of the list on every recursive call With larger lists this consumes too much space The following procedure uses the same idea but in a REPEAT instead of by recursion TO PICK N L REPEAT N 1 MAKE L BF L OUTPUT FIRST L END To compare the two we write a test procedure so that RL can be used to accept a list longer than a single line TO PICKOUT N L FT MAKE L RL MAKE N FIRST RL PICK N L PRINT RESULT END 123 ABCDEFGHtIJK LMN O P QRSTUVWXYZ 10 J By experimentation you will find that the first procedure PICK1 runs out of memory far sooner than the second PICK Why Because the amount of memory used by PICK1 depends both on the length of the list and on the number of items which must be peeled off the list the number of recursive calls The amount of memory used by PICK depends only on the length of the list The next proce
122. motion and continue in motion in the same direction until disturbed The two turning keys now change the direction of a thrust instead of changing the direction of the turtle directly The third key gives the turtle a thrust or push in the current direction The following version of RUNNER shows how this is done TO RUNNER X VX VY PU SX X SHAPE FFFFFFFFUBBBRRFD FFUBBBDBBB WHILE 1 1 MAKE X MAIL 1 IF 1 MAKE VX VX SIN HEADING ME MAKE VY VY COS HEADING ME IF X 45 RT 45 IF X 315 LT 45 SX XCOR VX SY YCOR VY END Here X 1 means there should be a move the current direction We move the turtle by a series of SX and SY commands the increments VX and VY are adjusted by use of the standard trigonometric functions SIN and COS To use this modified version of CATCHEM we have to make the above changes in CHASER as well as in RUNNER and we must set some initial values of VX and VY for both players The initial values are set in the procedure CATCHEM by adding numbers onto the procedure calls You might start with values about 5 and it makes a better game if the chaser is a bit faster than the runner The second game is called REBOUND It makes use of the game controllers The object of the game is to bounce a ball off two paddles onto a target Here we ll need a few more turtles We first assign four tasks reading of the two controllers a scorekeeper and a trigger to start the wh
123. mple the command ABSOLUTEVALUE 10 FD RESULT gives the desired action The OUTPUT command in ABSOLUTEVALUE transmits the new value and RESULT picks it up for further use 112 Given the availability of the ABS function the sample procedure is not really useful How ever there are a number of other mathematical functions which might be of use For example Super LOGO does not supply a function for raising a number to a power The following proce dure supplies it TO EXP NUMBER POWER X MAKE X NUMBER REPEAT POWER 1 MAKE NUMBER NUMBER lt X OUTPUT NUMBER END Try this out with the commands FT EXP 2 3 PRINT RESULT 8 FT EXP 6 3 PRINT RESULT 216 square root function is even possible as long as you allow for the limited accuracy of the division operation The following procedure makes use of a common process of successive approximations for the square root of a number TO ROOT N G IF N lt PRINT NEGATIVE STOP MAKE G N 2 WHILE ABS G G N gt 1 N 16 MAKE N G 0 5 OUTPUT G END Try this out with the following be sure to hide the turtle first Note Clear the screen between answers or a shorter answer will retain the last digit of a longer answer Bo Shes ROOT 10 PRINT RESULT 3 41 ROOT 100 PRINT RESULT 10 05 ROOT 10000 PRINT RESULT 101 48 113 While the accuracy is limited by division it is sufficient for calculating the distance between
124. n for W in this list This result is used by INSERT to update the list in NEW If you want to follow the process insert the command PRINT NEW after the command MAKE NEW RESULT 131 The next step is to write the procedure COMPARE TO COMPARE WORD NEW W1 N MAKE N 1 WHILE NEW lt gt MAKE W1 FIRST NEW COMPWORD WORD W1 IF RESULT MAKE N N 1 MAKE NEW BF NEW ELSE OUTPUT N OUTPUT N END This procedure compares a word and the words on a list by taking words from the list in order and using the subprocedure COMPWORD as yet unwritten to compare the two words If WORD precedes the word from NEW W1 then COMPWORD should return FALSE so that COMPARE will output the current value in N If WORD does not precede the word from NEW then COMPWORD should return TRUE so that COMPARE will increment the value in and move ahead to the next word in the list If the list is empty WORD belongs at the end of the original list and the value in N points to the end of that list Finally we must actually make the comparison of the two words and send output as described above COMPWORD W1 W2 IF W1 W2 OUTPUT TRUE WHILE FIRST W1 FIRST W2 1 BF W1 MAKE W2 BF W2 IF ASCII FIRST W1 ASCII FIRST W2 OUTPUT FALSE OUTPUT TRUE END First we check to see if the two words are the same If they are their order in the list does not matter and we arbitrarily outp
125. n turn Of course 1 CLEAR will clear the screen so you won t have much time to see that one Note the correspondence between the symbols on the keys the symbols on the bottom of the screen and the action of the turtle Now that you have a bit of the idea of DOODLE mode let s try to make something useful To get a fresh start exit DOODLE mode by pressing BREAK This puts you in BREAK mode Clear the procedure space by pressing CLEAR Get into the RUN mode press then get into the DOODLE mode press reason that we always get into the DOODLE mode from RUN mode is that we may want to draw patterns on the screen RUN mode for the child to interact with or copy in DOODLE mode Notice that the screen is not cleared when we enter DOODLE mode Now let s name the procedure we are creating S by typing an S and pressing ENTER 55 by drawing box using the top row of keys When the box is completed exit DOODLE mode by pressing the key Then get the RUN mode and run the procedure s The only difference between this and the procedure we earlier called BOX is that S is a little slower To see that S actually exists as a procedure get into EDIT mode and look at procedure S Notice that it is there with exactly the symbols used in its definition We can actually edit S in EDIT mode just as we edit any other procedure For example we can add a diagonal to a box in several ways First
126. name used to describe unique storage locations where numbers letters words or sentences can be this chapter we ll use variables only for keeping numbers We specify the contents of a variable by typing a colon 2 followed by any number of letters and or numbers Variables can be used anywhere numbers can be used By using variables in place of numbers we can make our procedures useful in a wider variety of applications For example we can make our SQUARE procedure draw squares of many sizes TO SQUARE SIDE REPEAT 4 FD SIDE RT 99 END If you came here directly from the last chapter then there is another version of SQUARE in memory To clear out the memory press SHIFT CLEAR while you are in BREAK mode Then get into the EDIT mode and enter the new version of SQUARE Now to run SQUARE get into RUN mode and enter SQUARE 40 Because we have listed the variable SIDE on the TO statement we must give a value when we call or use the procedure SQUARE Now try a variety of other numbers for instance SQUARE 60 SQUARE 20 Notice that the computer takes the number which follows the procedure name SQUARE sees that that number is the value of the variable SIDE and uses that number every place the variable SIDE appears within the procedure What happens if we forget the number Try SQUARE If we don t provide number then the computer provides a zero The brief flicker is due to the turtle turning in place
127. nd The form of the command is HATCH turtle number procedure for the turtle or to give a specific example of the format HATCH 1 BOX 50 30 60 HATCH needs to be used inside a procedure so don t try out the command just yet or the command will be ignored Here the meaning of HATCH is obvious The first number here 1 is the name or label of the turtle Turtles can be labeled with any number between 1 and 254 Turtle 0 is the master turtle always present even if hidden by HT command which we have been using exclusively up to now BOX is the name of the procedure which we are tell ing turtle 1 to run The numbers following BOX are as usual the values to be fed into the local variables within BOX Next wetry out a simple multiple turtle program Enter the following TO TESTI HATCH 1 BOX 50 30 60 HATCH 2 BOX 40 180 90 HATCH 3 BOX 60 100 90 END 77 Notice that each turtle has its own procedure and its own set of values for the variables course several turtles can be using the same procedure but each still has its own current set of values for the variables When you run TEST1 you may get less than you expected Why does the program stop before drawing the boxes Notice that there are four turtles on the screen the three you created with the HATCH commands and as always the master turtle When there are multiple turtles Super LOGO gives each turtle a turn in sequence A turn is single turtle command or a logi
128. ng it down will cause the current dot to be complemented Notice that because the only move forward or back possible is one dot then the smallest turn which makes sense is 45 degree turn This will be clearer if we give an example Let us assume that the current orientation of the turtle is heading straight up Then the command SHAPE URRFFFLLDFFFFL FFFLLFFFLFFFF will draw the following turtle shape 87 Notice that the turtle shape commands extend over more than single line Multiple lines must be connected with a hyphen and must start in column 1 This in turn means that there is no limit on the size or complexity of a turtle shape However the turtle shape must be redrawn every time the turtle moves so the larger and more complex the turtle shape the slower the system will run It is fairly difficult to create desired turtle shapes by trial and error at the keyboard It is especially difficult to locate an error in the middle of a string of turtle shape commands We have found the following to be effective ways to proceed First design the turtle shape on a piece of graph or engineering paper The possibility of rotating the paper as you enter the shape may save you from getting a stiff neck trying to play turtle at the keyboard Once the shape is designed on the graph paper there are two methods which we use If the turtle shape is a simple one enter the shape DOODLE mode Remember that the keys 3 4 5 6
129. ns on the screen the result of such procedures is a track and a final turtle position and heading on the screen Although numbers were sent from a higher level procedure to a lower level subprocedure for example by commands like BOX 50 no information was sent back from the subprocedure to the higher level procedure But in other applications information must be sent both ways In this chapter we will learn to return results from subprocedures to higher level procedures In the process we will learn a bit more about variables The primitive commands thus far can be separated into two classes In one class we have the commands which can be executed on their own without any additional information The following commands require no additional information PU PD ST HT CLEAR DRAW SPLITSCREEN Other commands require additional information before they can be executed FD BK RT LT PC SX SH Each command in the second set needs a number to become a functional command for example FD 30 BK 40 RT 90 LT ANGLE PC 1 etc Most functions for example MAIL NEAR RANDOM FIRST LAST also need more information usually called an argument to operate MAIL 2 NEAR 3 RANDOM 5 FIRST L etc Notice that the functions not only require an argument but that they also produce a result that could be used as an argument for another function MAIL FIRST L NEAR RANDOM 5 RANDOM MAIL 2 NEAR FIRST L When we need an operation which LOGO does not include as a prim
130. ns until it finds BIGDOT a second time To search for the third occurrence enter SHIFT ENTER and so on complete list of operations available EDIT mode is contained the EDIT mode section of Appendix I 75 16 MULTIPLE TURTLES So far we have been drawing on the screen with a single turtle Complex figures were made by drawing one at a time first plece completely then a second piece and so on until the drawing was complete In Super LOGO there is another way to produce a complex draw ing We can draw all the parts at once using several turtles Multiple turtles provide many possibilities Games are one obvious application It is much easier to program games if each player is assigned a turtle which maintains its position until that player s next turn In other applications we can make drawings by assigning to turtles the tasks of drawing individual pieces of the whole In this way the drawing will seem to evolve instead of appearing piecemeal At a more serious and abstract level we can use the multiple turtles to illustate the process of multiprogramming Let s begin by entering a few procedures for the turtles to run Clear the memory and enter TO BOX SIDE X Y SX X SY Y REPEAT 4 FD SIDE RT 990 END TO CIRCLE SIDE X Y SX X SY Y REPEAT 20 FD SIDE RT 18 END Run each of these to verify that they are entered correctly We create new turtles by means of the HATCH comma
131. nto two lines at the cursor location SHIFT deletes the character under the cursor and moves the remainder of the line left to close the gap If the line has no characters then the blank line is removed SHIFT inserts a blank into the line at the cursor location by moving the remainder of the line right one space If the line is already full then no action takes place SHIFT CLEAR deletes from the cursor position to the end of the line If the cursor is in column 1 the entire line is removed from the text 163 SHIFT is used in one of several ways to move quickly forward in the text When this key combination is pressed the cursor moves to the very bottom line on the screen The user has three options of what to do next The first possibility is to press again This causes the text lines to scroll up continuously The text lines continue to scroll until a key is pressed or until the last line of the text is reached The second possibility is to enter a search string The search string may be up to 16 characters Next press the key The text lines scroll up until a line containing the search string is located or until a key is pressed or until the last line of text is reached The third possibility is to just press the LENTER key again This produces another search for the s arch string most recently entered Thus to find the first occurrence of the word BLUE the user would press SHIFT and enter the word BL
132. nts to be passed If arguments are present they are separated by one or more spaces Each argument may be a number variable word list function reference or an expression contained in parentheses argument s values passed to the parameter variables on the TO statement of the called procedure If there are fewer arguments than there are parameters on the TO then extra parameters set to 0 If the called procedure executes a STOP OUTPUT or END then control continues with the next statement after the call statement 169 REPEAT expr list of stmts SEND expr expr SLOW expr STOP TEST expr TEXT expr TO procname parmlist TRACE 170 The expression 1s evaluated if it has a value less than or equal to zero then the list of statements is skipped Otherwise the list of statements is executed the specified number of times message 15 sent to the specified turtle The first expres sion value denotes the identification of the turtle to which the message 1s sent value of 255 denotes that the message 15 being sent to the first turtle that requests its mail Any other value denotes that the message can be received only by a turtle with the specified identifica tion see also the MAIL function The value of the sec ond expression is the value sent to the other turtle The SLOW statement causes execution to slow down so that it can be watched more closely The value of the expression deno
133. o PM LEARNING TO USE AN EDITOR Again position the cursor at the start of BEGINNING and overtype the characters you want to change Here the problem is that an extra N remains To delete a character or space hold down the SHIFT key and press the left arrow key Try it and remember press SHIFT left arrow to delete Poor Grandma isn t going to know who the note is from unless we add a line at the end Use the up arrow key to move the cursor as far down as you can It should be at the start of a blank line following the text We want to skip a line before signing the note so press ENTER once Notice that when you press ENTER a line is added at the end But if the cursor is within the text pressing ENTER has the same effect as the up arrow Now space over and sign your name While we are at it we should skip a line after DEAR GRANDMA That is we want to change DEAR GRANDMA M LEARNING TO USE AN EDITOR LOVE ANN 16 to DEAR GRANDMA PM LEARNING TO USE AN EDITOR LOVE ANN Position the cursor at the beginning of the line PM Then hold down the SHIFT key and press the down arrow key Move the cursor down to check that you got what you wanted Remember to insert a new line position the cursor at the start of the following line then press SHIFT down arrow We want to make one more change We want to change the closing to LOVE ANN We want to break one line into two Position t
134. o have the turtle draw a pattern in one quadrant and to have the child complete the pattern in the other three quadrants Either DOODLE mode or the OK Set can be used here If you ve included the erase procedures for the DOODLE turtle commands in the OK Set then that set is preferable A simple pattern is TO 4 CLEAR RT 90 REPEAT 2 FD 60 SX 128 SY 96 RT 45 HOME END 67 We have written the procedure so that it is easy to add lines to make more elaborate pat tern However we recommend that you restrict the patterns to those using angles which are easy to produce in DOODLE mode that is multiples of 15 or 45 degrees We reset the turtle to the home position with the SX and SY instead of with HOME so that the turtle heading is preserved Again the FD should be some multiple of 10 to minimize the number of keystrokes needed This gives a more complex pattern TO PATTERN5 CLEAR LINES 60 128 10 HOME END TO LINES LENGTH X STEP IF LENGTH 0 STOP SX X SY 36 SH 0 FD LENGTH RT 90 FD LENGTH LINES LENGTH STEP STEP STEP END 68 gt a zs 8 E aee i T starting points for the pattern picked so as to center the pattern the home position Thus because home 15 at 128 96 the starting point for the first line is at 128 36 which is 60 units below home We ve chosen to orient the pattern so that the child begin drawing wit
135. oduced the following section of the procedure MAKE C Y WHILE P lt 22 amp C Y PRINT CARD MAKE C RC IF C Y MAKE PLAY SE PLAY FIRST L MAKE L BF L PRINT PLAY CHECK PLAY MAKE P RESULT Now we check to see if the player has lost IF P gt 21 PRINT DEALER WINS If not then the dealer must play according to commands following the ELSE WHILE D 17 MAKE DEAL SE DEAL FIRST L MAKE L BF L PRINT SE DEALER DEAL CHECK DEAL MAKE D RESULT The strategy for the dealer is to continue to draw until the value of the hand is 17 or greater regardless of what the player has This seems like a very simple strategy in fact it is what most casinos use as close to the optimum for the dealer The last few steps are straightforward We check to see if the dealer s total is too high and if not who has the higher total There are some obvious extensions we could add to the procedure We have not kept score and this would be easy to do We have only allowed one pass through the deck in fact an incom plete last hand will make the computer do strange things We could have the condition on the first WHILE check to see that there are enough cards for two hands about 10 or if we wanted to get fancy we could reshuffle with a deck minus the cards in play These additions would make the game closer to the standard game but they would not increase our knowledge of Super LOGO much so we
136. ole thing off 102 REBOUND CLEAR 2 PADDLE1 3 PADDLE2 HATCH 6 SCOREKEEP TRIGGER END Let s look at the paddle controls first The paddles can be turned to direct the ball to the target TO PADDLE1 HT SX 60 SY 180 TURN 0 END TO TURN P X WHILE 1 1 MAKE X PADDLE P 2 LINE 3 SH 45 3 X LINE WHILE PADDLE P 2 X END TO LINE COLOR PC COLOR FD 15 BK 15 BK 15 FD 15 END PADDLE1 establishes the position of the first paddle on the screen It calls TURN which actually reads the game controller The new idea in TURN is the use of the PADDLE func tion The PADDLE function returns a number between 0 and 63 for the designated input the number depends on the position of the controller handle The inputs are 0 and 1 for the horizontal and vertical positions of the left game controller and 2 and 3 for the horizontal and vertical positions of the right game controller Thus PADDLE1 by the instruction TURN 0 tells the procedure TURN to read the horizontal position of the left controller left refers to the position of the plug on the rear of the Color Computer Because the instruction is MAKE X PADDLE 2 the variable X holds a number between 0 and 31 This division of the controller reading by 2 reduces the sensitivity of the display and speeds response Notice that after the first pass through TURN the procedure looks for a change in the controller setting It stays in
137. ollowed by ENTER the cursive letter will be drawn Or one could de fine a procedure with a word spelled out spaces between the letters and the result would be the word in cursive letters TO CURSIVE END will write in cursive if the procedures C and T are correctly defined make it all work smoothly the turtle will have to end up in the right position after each letter If that is not enough of a challenge then how about making the computer draw letters as they appear in a manual on calligraphy No doubt you will have to make them a bit bigger to get the desired effect The only limitation is that you can t have both upper and lower case letters at once There are limits even with Super LOGO 72 This chapter has given some idea of what be done with the Set DOODLE mode At this point there are several ways you might continue with a child One is to continue with DOODLE mode giving them ever more challenging tasks or encouraging them to create useful procedures which you help them use in RUN mode If they are reasonably good with the key board they may not need much help An alternative is to teach them how to extend the OK Set by adding procedures they create in DOODLE mode they can make their own key labels and attach them as they name the procedures For example you could suggest that they draw a truck a house a tree and a person in DOO DLE mode and then let them draw street
138. on we decide to alter the note so we return to EDIT mode press E The first line of our note appears with the cursor at the start of the line 15 We decide to change the word STARTING the second line of the note to the word BEGINNING To do this we first must display the second line and position the cursor under the S in STARTING We move the cursor by use of the arrow keys Up arrow and down arrow move the cursor to a different line and left arrow and right arrow move the cursor within a line Changing lines always resets the cursor to the start of the line Arrow commands which make no sense are ignored Thus if we press right arrow when the cursor is under the comma follow ing GRANDMA nothing happens because there no more characters on the line Let s go through this step by step To see the second line of the note press the up arrow key once Then press the right arrow key several times to position the cursor under the STARTING Then type BEGIN Notice that the overtyping simply replaces the letters Now we have another kind of change to make because BEGINNING has one more letter than STARTING We want space for another N before the ING To create a space we hold down the key and press the right arrow key Now we can type the extra N in the created space Remember to insert press right arrow to create the space then type what you want Next let s change the line from PM BEGINNING TO USE AN EDITOR t
139. ored they change color Your Tandy Color Computer offers two color sets or settings in the high resolution screen on which turtles live Up to now you have been running in color set 0 You can shift color sets by the COLORSET command Get into the RUN mode and enter COLORSET 1 to change color set Then enter COLORSET 0 to change back Within each color set there are four colors numbered 0 1 2 and 3 The normal drawing color is color and the normal background color is color 3 Change the background color by entering BACKGROUND 1 or abbreviate BG 1 Change the pen or drawing color by entering PENCOLOR 2 or abbreviate PC 2 You can erase a portion of a drawing by making the pen color the same color as the back ground color and drawing over the unwanted part of the drawing Let s add color to some of our earlier procedures One interesting choice is FOUR Retype BOX see p 21 then enter the procedure FOUR as TO FOUR REPEAT 2 PC 1 BOX PC 2 BOX END and to allow easy experimentation make MANY into TO MANY N REPEAT N FOUR RT 90 END 33 We would like to able to name the colors you will get with specific colors and color sets but colors vary from TV to TV they vary with the color settings on the TV and they may even switch when you restart your computer Try running MANY from page 33 with a value of 10 Then adjust the color and tint controls on y
140. oup It might help to give them objects to actually walk around to make the shape less abstract One heavily used technique in early childhood teaching is to ask the student to copy some thing A book titled Mathematics Their Way by Mary Baratta Lorton Addison Wesley Publish ing Company 1976 makes use of this technique for beginning mathematics and is a rich source of ideas for DOODLE mode projects Basically the approach is to write a procedure which will draw a figure or shape This can be placed on the screen in RUN mode The child is then asked to copy complete fill in invert rotate or in some way proceed with reference to the figure on the screen If the procedure the child develops while doing this is likely to be worth keeping for future use then the child should be working in DOODLE mode If it is not worth keeping or if it requires the more complex shapes then the child should be working with the OK Set of procedures Let s turn now to some specific activities A large number of exercises could be built around the idea of pattern continuation and generalization These activities are best suited to the OK Set so the following procedures should be added to that set One of the simplest types is a pat tern which can be imposed on a line of dots First we draw two parallel lines of dots 63 DOTS CLEAR HT RT 90 SX 5 SY 150 LINE OF DOTS SX 5 SY 50 LINE OF DOTS END TO LINE OF DOTS REPEAT 26 BIGDO
141. our TV set to your satisfaction On many color set 1 will give more interesting colors so be sure to try that too You can change color sets without redrawing the figure by typing COLORSET 1 Manr 10 COLORSET 1 An interesting variation can be created by the following changes TO BOX 1 50 RT 90 2 30 RT 90 50 RT 90 1 30 END 34 FOUR 4 END TO MANY N REPEAT 2 3 FOUR RT 90 N END Try it with N 90 Ifitistoo slow or if you feel sorry for any turtle that has to run around at that speed for so long hide the turtle HT before calling MANY 99 You might prefer the colors you get with dark background Try setting the background to 0 and rerun the preceding two examples MANY 10 and MANY 90 35 9 OTHER TURTLE COMMANDS There are a few additional turtle commands which we have not yet used We can raise and lower the turtle s tail so we have the choice of leaving a track or not leaving a track The com mands are just what you d guess PENUP abbreviated PU and PENDOWN abbreviated PD Let s illustrate by removing the lines of one color from the previous figure Change BOX to TO BOX PU FD 50 RT 90 PD PC 2 FD 30 RT 90 FD 50 RT 90 PU FD 30 END and again run MANY 90 Every figure so far has started in the center of the screen at a position called home When we get into the RUN mode the turtle automatically moves
142. parent or teacher will have to assist them in learning In this and the next chapter we will teach the assistant the mechanics of two ways to use Super LOGO with children actual suggestions for activities with the children are gathered together in Chapter 14 In this chapter we will cover the mechanics of DOODLE mode The idea of DOODLE mode is that a minimum set of turtle commands can be entered by single keystrokes from the keyboard Before proceeding you should get the plastic overlay for the keyboard which was supplied with the Super LOGO package This overlay fits over the top row of the keyboard The symbols on the overlay show the meanings of the numeric keys in DOODLE mode see Appendix These symbols will appear at the bottom of the screen in DOODLE mode when the keys are pressed and they will appear in the procedures that you create in DOODLE mode You can get into DOODLE mode by first getting into RUN mode then pressing the key When the e key is pressed an appears at the bottom of the screen This is the indication that it is time to name the procedure you are creating Simply type the name you want to use the name can be as simple as a single letter or number After typing the name press ENTER The computer is now in DOODLE mode and the top row of keys has its new meaning The meanings of the keys are 1 CLEAR 2 HOME 3 PENUP 4 PENDOWN 5 RT 45 6 LT 45 7 FD 1 8 FD 10 9 RT 15 LT 15 Try each of the keys i
143. part 0 45 90 In DOODLE mode the only steps forward possible are one unit and ten units We ve already said that the only turns that are useful with one unit forward are turns which are multiples of 45 degrees With ten units forward turns as small as 5 degrees give consistent visible results but these seem too detailed and require too many keystrokes for the typical DOODLE mode user Therefore the smallest turns provided are multiples of 15 degrees If you want to make a line at some other angle in DOODLE mode you can It just requires more keystrokes The combination of FD 1 operations and either no turn or a turn of 45 degrees will allow the drawing of a line at any angle For example a very small angle could be drawn by repeating this series the desired number of times FD 10 key 8 followed by nine FD 1 s key 7 an RT 45 key 5 an FD 1 and an LT 45 key 6 This sounds awkward but remember that it will be necessary very seldom Most young children will find sufficient accuracy with turns of 15 and 45 degrees DOODLE mode characters are not available on printers If you try to print a procedure created in DOODLE mode the special characters will appear as lowercase letters Thus it is imprac tical to print DOODLE mode procedures Also notice that the character has a special mean ing in EDIT mode If you want to include an character in a line of a procedure to prevent a line feed when printing you must press twice
144. points on the screen Notice that we include a trap for negative numbers The accuracy can be increased within a more limited range of numbers by adjusting the condition on the WHILE but if you try for too much you will end up in an endless search The next step is to combine some of these procedures For example we might want to compute the square root of 5 raised to the 3rd power If you have entered the procedures EXP and ROOT the following line will print the correct result EXP 5 3 ROOT RESULT PRINT RESULT 11 46 Notice that the line reads exactly in the order that the computer does the operations To make sure you have this straight we ll give another example If we want to print 5 raised to the 3rd power and then multiplied by 6 we enter CLEAR FT EXP 5 3 PRINT 6 RESULT 750 these examples we ve used the MAKE command several times Look at the example MAKE G N 2 In the last chapter we learned that the notation G indicates the word G Variable names are words any word can be a variable name The notation N designates the contents of the varia ble with the name N The contents of a variable are completely distinct from the name of the variable The name must be a word but the contents may be a number a word or a list The next procedure takes advantage of this difference TO PHONEBOOK MAKE DENNIS 555 3958 MAKE JOE 555 9935 MAKE CHRIS 555 9965 MAKE ELAINE 555 7563 END
145. portunity to show one way to attack such a problem However you must realize that this is only a potentially useful suggestion not a foolproof method for deal Ing with every recursive problem The first thing we realized was that we would need a procedure to switch two letters in a word Of course this 16 not the top down process we advocated in Chapter 6 but that is a tech nique not a rule The following procedure switches letters in positions P1 and P2 of the word W The assumption is that P1 comes before P2 TO SW W P1 P2 L J1 J2 T MAKE 1 MAKE J2 MAKE L 1 REPEAT P2 1 IF L P1 MAKE WORD J1 FIRST W IF L P1 MAKE T FIRST W IF L gt P1 MAKE J2 WORD J2 FIRST W MAKE W BF W MAKE L L 1 1 WORD WORD WORD WORD J1 FIRST W J2 T BF W OUTPUT J1 END To switch two letters within a word we have to divide the word into five pieces the letters in front of the first switchable character in J1 the first switchable character in T the letters between the two switchable characters in J2 the second switchable character FIRST W after the others are peeled off and the rest of the word BF W The procedure SW uses the REPEAT with IF conditions to peel off the first three pieces and then puts the new word together with four WORD operations Next we wrote procedures for the simple particular cases The simplest case to handle is a two letter word There ar
146. r from whatever its current heading is We telling the turtle how to change its heading we are not telling the turtle to head toward some point In the same way when we tell the turtle to go forward we are telling the turtle how to change its position we are not telling the turtle to go to some point on the screen Thus the position and heading of the turtle after one of these commands will depend on where the turtle started So far we have learned three primitive turtle commands Papert would say three words in turtle talk They are CLEAR FORWARD and RIGHT With these three we can draw figure which will fit on the screen and which could be drawn on paper without lifting the pen cil from the paper You might try drawing a triangle three sided figure and a pentagon five sided figure for practice If you re like us you don t remember the angles for pentagons so experiment We could go a long long way with just RIGHT and FORWARD but LEFT and BACK are useful too Clear the screen and try LEFT 90 We could have used the abbreviation LT for left turn Now let s make the turtle move back wards Try BACK 46 or in abbreviated form 40 Notice that the turtle is somewhat transparent You can see the track through the turtle If you d rather not see the turtle at all you can hide it Enter HIDETURTLE the abbreviation is much shorter turtle is still there but it is invisibl
147. r LOGO program is available in three versions The Disk version 26 2716 requires a 32K disk based Tandy Color Computer with Color BASIC The Network 2 version 26 2738 is designed for use with a Tandy Network 2 Controller a 32K disk based Tandy Color Computer as host system and from one to sixteen 32K disk or cassette based Color Computers as student stations The ROM version 26 2717 requires a 16K ROM based Tandy Color Computer with Color BASIC Procedures that you write can be saved on diskette or on cassette tape using the Disk version on cassette using the ROM version or on a dis kette at the host computer using the Network 2 version 1 ABOUT Super LOGO Super LOGO is computer language for children Like the best things for children Super LOGO can provide endless fascination and challenge for adults as well At first glance Super LOGO may seem to be simply a language for drawing pictures because the result of running the procedures in the early sections of the manual is almost always a picture However Super LOGO is far more than an easy way to draw pictures Super LOGO is a tool for learning about some of the most powerful concepts in mathematics physical sciences computer science prob lem solving and language syntax but in a way so appealing and simple that even a kid can do it Notice that we said that Super LOGO is a language for learning we very intentionally did not say that it is a language for tea
148. r scan delete from cursor to end of line search for a word 18 position cursor overtype position cursor SHIFT no effect if line full then type character position cursor SHIFT position cursor at start of following line position cursor at break point SHIFT t twice any key SHIFT CLEAR SHIFT t followed by the word followed by ENTER 5 PROCEDURES You have now mastered five primitive turtle commands CLEAR FORWARD BACK RIGHT and LEFT Next we want to combine these commands into a unit which we call a procedure The first step is to tell the computer not to obey each command as it is typed but to store the commands This is what happens in EDIT mode Press BREAK then hold down and press to clear the memory of old programs Then get into EDIT mode press The screen should be blank with the cursor in the lower left corner If the screen is not blank return to BREAK mode by pressing the key hold the ISHIFT key down and press the CLEAR firmly Return to EDIT mode by pressing E You are now using a line oriented editor We will practice using the editor as we create and edit procedures Our first exercise will be to write a procedure for drawing a rectangle First we must give the procedure a name We ll call this first one RECTANGLE The first line of the procedure contains the name and we let the computer know that we re naming a proce
149. ral other subprocedures We gave NTOWORD in the beginning of Chapter 23 we won t repeat it here The other two follow TO CARDTONUMBER CARD N MAKE N CARD IF CARD A MAKE N 14 IF CARD K MAKE 13 IF CARD Q MAKE N 12 IF CARD J MAKE 11 OUTPUT N END TO NUMBERTOCARD N CARD IF N 11 NTOWORD N MAKE CARD RESULT IF N 14 MAKE CARD IF N 13 MAKE CARD IF 12 MAKE CARD Q IF N 11 MAKE CARD J OUTPUT CARD END These two provide the conversion between the symbols we expect for cards and the number codes which can be sent between procedures as messages The preceding example illustrates techniques which can be used for a variety of card games Notice that we could have as many players as we wanted by use of multiple turtles In games which involve strategy separate procedures which implement different strategies could be written for each player and those strategies could be evaluated by the results Instead of doing exactly that we ll show a different type of game a game in which the user is one of the players This time one of the players is the computer so a strategy will be implemented in a procedure but the user is free to pick any strategy desired 139 The game is the game of blackjack 21 The rules simple the object is to get closer to 21 than your opponent without exceeding 21 The opponent is the dealer one of whose
150. re visible on the entire screen 165 FULLTEXT SCREEN FULLTEXT mode uses the entire screen for text only It is entered by the FULLTEXT or FT command and it is exited via the SPLITSCREEN DRAW or FULLSCREEN commands The turtle is invisible in FULLTEXT mode and lines are not drawn The entire screen becomes the text viewport This mode is normally used for text manipulation programs that do not use turtle graphics RUN MODE You can get into RUN mode from the BREAK mode by pressing R When RUN mode is en tered the screen is cleared and the turtle appears at the home position A text window of three lines exists at the bottom of the screen The user enters turtle graphics commands or calls Super LOGO procedures that have been entered earlier via the EDIT or DOODLE mode The user can enter any of the following commands directly in RUN mode Any number of com mands may be entered as long as they fit on one line Once the ENTER key is pressed the commands are executed COMMANDS WHICH CAN BE ENTERED DIRECTLY IN RUN MODE BACK BACKGROUND BAUD CLEAN CLEAR CLEARSCREEN CLEARTEXT COLORSET DOT DRAW ECHO FENCE FORWARD FULLSCREEN FULLTEXT HATCH HOME HIDETURTLE IFFALSE IFTRUE LEFT NOECHO NOTRACE NOWRAP PENCOLOR PENDOWN PENERASE PENUP PRINT PRINTSCREEN REPEAT RIGHT SEND SETHEADING SETPEN SETX SETY SHOWTURTLE SLOW SPLITSCREEN TEST TEXT TRACE VANISH WRAP Some of these commands may be abbreviated Other SUPER LOGO commands may not
151. rom the size of a tur tle step in the horizontal direction If you plan to use the TV mainly for LOGO you may want to adjust the set for this differenc By adjusting the Vertical Size Control you should be able to change the rectangle into a square However you must understand that this will affect the proportions of everything you display on the TV so don t make the change without considering other uses of the set Now that we have a way to repeat a short list of commands as often as we wish we can draw a series of regular polygons For example a triangle REPEAT 3 FD 60 RT 120 a pentagon REPEAT 5 FD 60 RT 72 11 REPEAT 6 FD 40 RT 60 REPEAT 6 CFD RT 603 Remember that you can use CLEAR as a command to start with a fresh screen whenever you want One of the most useful figures to draw is a circle The idea is that one draws a circle by mov ing forward a bit and turning a bit many times For a complete circle to be drawn the total of all the repeated turns must be at least 360 degrees Two different sized circles could be drawn by the following REPEAT 360 FD 1 RT 1 REPEAT 186 FD 1 RT 2 Many other combinations are possible The figures drawn above are really 360 and 180 sided polygons instead of circles They look like circles because of the finite resolution of the screen display In fact even cutting the num ber of sides down to 36 still gives a pretty good circle REP
152. rs in the next round The game is over when one player is out of cards When this happens the losing turtle will send a message to turtle 3 ENDER which will in turn send a message back to turtle 0 WAR The message from ENDER is kept in OVER The first WHILE WHILE OVER 0 continues to check until such a message is received from ENDER You might wonder why we used a separate turtle to keep track of the end of the game when the player turtles are already sending messages directly to turtle 0 It is easier to distinguish a game ending mes sage by its source from turtle 3 than to distinguish it from cards by its value Both players use the same procedure 137 TO PLAYER L COUNT N ME NTOWORD ME MAKE ME RESULT WHILE L lt gt NTOWORD COUNT PRINT SE SE ME HAS RESULT MAKE N FIRST L CARDTONUMBER N 0 SEND 0 RESULT MAKE 0 WHILE T 0 0 IF 15 MAKE L BF L MAKE COUNT COUNT 1 ELSE MAKE COUNT COUNT 1 NUMBERTOCARD T MAKE L SE SE BF L FIRST L RESULT SEND 3 ME END TO ENDER OVER WHILE OVER 0 MAKE OVER MAIL 255 NTOWORD OVER PRINT SE SE PLAYER RESULT LOST SEND 0 OVER END Let s take PLAYER step by step We want each player to report on the status of his or her hand at each step These are two independent procedures so we cannot rely on player 1 report ing before player 2 winning play requires more commands to process than a losing p
153. ry little code we still don t want to have to retype procedures every time we start up To avoid having to do this you can store procedures on cassette tape This chapter describes how to do so To move procedures to and from cassette we must be in BREAK mode By now you probably have a number of procedures in memory that you would like to keep Get into EDIT mode and delete any that you do not want to save The delete line operation will speed the deletion of unwanted procedures that is holding down the key and pressing the key deletes from the current cursor position to the end of the line To delete a whole line position the cursor at the start of the line and press Next get into BREAK mode use the key and press S At this point the prompt will be LOGO SAVE You now have to tell the computer where to save the procedures that are in memory Of course the tape recorder must be plugged in as described in the Operation Manual for the Tandy Color Computer Make sure that the volume control is set close to 5 Rewind the tape REWIND STOP Next press the RECORD and PLAY buttons so that they both stay pressed down If you are not using leaderless tape pull out the MIC plug for about 5 seconds This will make sure that you begin recording on blank tape Now you are ready to record the procedures Simply respond ENTER to the BREAK mode prompt LOGO SAVE When the recording is done the BREAK mode prompt will be displayed a
154. s and in turn to break each subproblem into even simpler subproblems until the subproblems can be solved by a single REPEAT statement Specifically we broke the original problem into the problem of drawing SQUARE CIRCLE six times we broke SQUARE CIRCLE into the problems of drawing a square and drawing a circle These last two problems were easily solved with a single REPEAT statement In general we follow this sequence in attacking a problem although we do not insist that the lowest level proce dure consist of a single REPEAT statement One of the reasons for using Super LOGO with children is that it is an excellent way to teach children a most powerful and useful general problem solving approach That approach 16 what we have just illustrated Basically it involves working from the overall view down to the details by breaking each problem into pieces Moreover there is no limit to the number of problems like the one given above that can be generated to give children practice in problem solving By reviewing the children s solutions for style and clarity and by comparing their solutions with other solutions of the same problem you can teach them that problems may have several equally good solutions but also that not all solutions are equally clear and under standable In a teaching situation give the students feedback on the style of their procedures as well as on the correctness of their procedures 28 7 VARIABLES Variable is the
155. s the turtle just keeps checking its mail until it gets a message from turtle 1 If we look back at GETKEYS we see that a message 1 meant to move Thereforeif X 1 the runner is moved forward 8 If at this point the message is not 1 then it must be either 45 or 315 The runner is turned right by either amount remember that RT 315 is the same as LT 45 This completes the move so the turtle goes back to checking its mail from turtle 1 Before going further look carefully at the arrangement of the two IF statements in RUNNER Notice that the parentheses after the first IF enclose the second IF and the ELSE This pairs the ELSE with the second IF The meaning is if X is not 0 the first IF then do one the other of the following if X is 1 move forward otherwise turn The CHASER procedure is similar to RUNNER but it includes the test for a successful catch TO CHASER X WHILE 1 1 HOME PU WHILE NEAR 2 12 MAKE X MAIL 1 IF X IF X 1 FD 16 ELSE RT X SEND 0 1 END CHASER includes nested WHILE statements The first one starts the chaser and runs for ever The inner one runs until a capture is made The definition of a capture is that the value returned by the NEAR function is 12 or less The portion of the procedure controlled by the condition NEAR 2 gt 12 is identical to that in RUNNER Remember that the NEAR func tion returns the total number of X and Y steps from the current turtle to the designated
156. s the integer portion converts each digit in turn and combines it with the previous digits to form the complete word The value 0 is treated as a special case 129 Now the program to generate the Fibonacci series is quite simple TO FIBONACCI L T N FT PRINT L REPEAT T MAKE LAST L LAST BL L NTOWORD N MAKE L SE L RESULT PRINT L END To try this out we must feed it a two term list and the number of terms we want generated For example try FIBONACCI 1 1 10 1 1 EE 112 9 T2 9 1 229 58 2 553831 13 171 222 55671321 11293581321 34 11235 8 13 21 34 55 112358 13 21 34 55 89 1123 5 8 13 21 34 55 89 144 The procedure first prints the starting series Then it repeatedly selects the last two terms from the series LAST L and LAST BL L and adds them The resulting number is con verted to a word and added to the end of the list You ask for any number of terms you like but after about 22 you have exceeded the capacity of the computer remember the largest number possible is about 32000 and the results become erratic Sorting is another list operation which is useful and simpler than forming sentences We could use the above conversion subprocedure in a procedure for sorting a list of numbers but for variety we ll work on alphabetizing a list of words Because words can be made up of digits and because the digits are ordered in the ASCII sequence the procedures will sort numbers as well
157. s the right bracket Several lists are shown below ONE TWO THREE FOUR 1 2 3 4 THIS SENTENCE IS A LIST OVER 556 ELEPHANT RALPH LJ X REMOVE The last two examples show that a list can contain as little as a single word and that a list can be empty 107 There two limitations which the words lists Super LOGO maximum length of a word is 13 characters Lists consists of words not of other lists We can try out the simple word and list functions without entering procedures Get into RUN mode The basic command to check the result of one of these functions is the PRINT com mand The PRINT command prints at the current position of the turtle without moving the turtle This can get confusing if we do several PRINT commands in sequence By entering FULLTEXT we convert to a pure text screen The text window which usually occupies only the bottom four lines of the screen then occupies the whole screen and the PRINT command prints on the next available line So enter FULLTEXT As a first step enter the command PRINT ABSOLUTE ABSOLUTE and notice that the word ABSOLUTE is printed on the next line Next try the FIRST function PRINT FIRST ABSOLUTE A Because the object of the function is a word FIRST returns the first letter of the word as a new word Try PRINT FIRST FIRST ABSOLUTE A The BUTFIRST function produces what its name implies Try PRINT BUTFIRST
158. same as before TO SCOREKEEP SCORE HT SX 200 SY 180 WHILE 1 1 PRINT CHAR 32 CHAR 32 PRINT SCORE WHILE MAIL 5 0 MAKE SCORE SCORE 1 COLORSET 1 COLORSET 0 END These two examples should help you to implement your own ideas for more complex games 106 19 WORD AND LIST OPERATIONS The origin of LOGO can be traced to the field of artifical intelligence The main goal of com puter scientists in the field of artifical intelligence is to design programs which will make a computer appear to have what a human being would describe as intelligence This is an extremely difficult problem One part of the problem is to make the computer understand English or German or Japanese or whatever The LISP computer language on which LOGO was based was designed for the manipulation of words and sentences for this purpose Super LOGO includes operators and functions drawn from LISP for the manipulation of words as well as numbers In this chapter we ll learn about the primitive functions The arguments of the functions are called words and lists A word in LOGO is similar to but somewhat more general than a word in English In LOGO a word is a series of characters ended by a space In English a word includes only the 26 letters and not all combinations and sequences of the letters are allowed as words In LOGO almost all characters which can be entered from the keyboard can be part of a word and there are no rules which limit the com
159. sasa sssi 77 17 New Shapes for Turtles 87 18 Turtle Games seit eite e cette eoe een e eee eee ian ee 97 19 Word and List 107 20 Communication Between Procedures 111 21 Interactive Procedures 117 22 Playing with Words Sentences 123 23 Generating and Sorting Lists 129 24 Card Games ss ccs scsccacesscccecessesccccsscsseeshtcasmesesasauasane EEan 135 29 Word Gani 145 DG DICE 149 S n s sis 153 Appendix Language Summary 2 161 INTRODUCTION Radio Shack Super LOGO is an educational computer language The language can be used to draw pictures the computer s video display using a shape on the screen called a turtle and it can be used to manipulate lists of words The graphics portion of Super LOGO is designed to let children learn by exploring Children plan an action then enter simple commands that move the turtle forward or back or turn it in any direction Here are a few of the special features of Super LOGO e Line oriented editing allows you to write and save sequenc
160. save only a portion of the procedures in memory you must first enter EDIT mode to insert the markers The marker for the start is gt gt and the marker for the end is lt lt Once these two are in place do a regular SAVE S and T If you want to run the procedures still in memory you first should return to EDIT mode to remove the markers Note that with the MERGE and the partial SAVE operations you can build new modules which contain any combination of procedures selected from other modules without retyping any of the procedures If you have a printer for your Color Computer you can print all the procedures in memory Again it is all or nothing except that you can interrupt the printing by pressing without damaging or losing the programs in memory To print connect the printer as described in the Owner s Manual load the paper and turn on the printer You may have to reset the baud rate to get the printer to work properly The baud rate is the rate at which the computer sends characters to the printer the computer must transmit at the rate the printer expects If the baud rate is wrong the printer will print but it will be gibber ish To reset the baud rate get into RUN mode and enter BAUD number number should be replaced by one of the numbers in the right hand column for baud rate use number 300 180 600 87 1200 41 2400 18 42 Consult the manual for your printer to find what rate it wants
161. scenes using these additions to the OK Set Of course they ll soon want to add color To do that they ll have to learn how to insert PC com mands into their procedures and before long they ll be typing and editing in the standard way 73 15 ADDITIONAL EDITING FEATURES There are some additional features of the editor which are useful when we have longer sets of procedures to edit We ll introduce them in this chapter There is a way to delete more than one character at a time When you are m EDIT mode that is holding down the key and pressing the key deletes from the current cursor position to the end of the line If the cursor is at the left mar gin this operation deletes the whole line Before you try this make absolutely certain that you are in EDIT mode because these same keys clear memory delete all lines in BREAK mode The SHIFT combination initiates one of several fast forward sequences The first response to the combination is that the cursor is moved to the bottom of the screen At this point the computer waits for additional input from the keyboard This input can be of three types One possibility is to enter the SHIFT combination a second time This causes the text lines to scroll up until the process is interrupted or until the end of the procedures in memory is reached You can interrupt the process by pressing any key A second possibility is to enter up to 16 characters This string of 16 characters becomes a
162. se lines could contain turtle tracks or even turtles The scrolling up will mess up your pat tern and at times might make it appear that there are two turtles Therefore avoid giving more than three lines of commands when using the full screen The easiest way to return to split screen is to press BREAK and then return to RUN mode Super LOGO is a structured language complex program written in Super LOGO could have the following structure Each letter within a box represents a procedure each line of type on the page includes the subprocedures of a particular level the lines indicate which subprocedures are used by each procedure There are four levels of procedures within this program The master procedure level 0 might use the subprocedures of level 1 in the order B C D C Subprocedure B might use the subprocedures of level 2 in the order E F E subprocedure C might use the subproce dures of level 2 in the order G F H etc Notice that subprocedures can be used many times and many places within the overall program 25 So far our examples we been working from the bottom up defining first procedure then writing a second procedure that uses the first procedure as a subprocedure etc That is typical of programming manuals where the emphasis is on the mechanics of a language Instead of on problem solving It is interesting to adopt that approach with Super LOGO at times because the results are often unpr
163. search string That is the computer searches through the procedures in memory starting from the current cursor position for an occurrence of the search string If a copy of the search string is found the search is stopped at that point Otherwise the search continues to the end of the set of procedures in memory This possibility can be used to locate errors for example mistyped procedure names or simply to skip ahead to a known procedure name The third possibility is to press ENTER This tells the computer to reuse the previous search string and to look for its next occurrence This process can be repeated as often as desired Notice that if you press ENTER after the first time you use the SHIFT combination you are telling the computer to search again for no characters which it will find immediately This sounds silly but it is easy to press ENTER inadvertently especially when nothing seems to be happening To make sure that you know how to make use of this very useful feature we ll give a specific example We ll assume that you saved the procedures from last chapter and that you want to locate all occurrences of the procedure named BIGDOT With the procedures in memory get into the EDIT mode and enter SHIFT BIGDOT ENTER Remember SHIFT means two keys and ENTER means key The computer will scan down through the procedures until it finds BIGDOT To find the next one enter ENTER Again the computer sca
164. shuffle the deck we ll proceed as follows The list containing the deck will be rotated a random number of times by rotating we mean take the first item from the list and place it at the end of the list The first card will be transferred to the end of the shuffled list and the whole process will be repeated with a deck one card smaller TO ROTATE N L REPEAT 1 MAKE L SE BF L FIRST L OUTPUT L END TO SHUFFLE N L l J PRINT SHUFFLING MAKE J REPEAT N ROTATE 1 RANDOM 1 L MAKE L RESULT MAKE J SE J FIRST L MAKE L BF L MAKE I 1 41 OUTPUT J END ROTATE outputs the rotated list SHUFFLE builds the shuffled list in J Notice that the argument for RANDOM must be adjusted as the unshuffled list becomes shorter SHUFFLE outputs the shuffled list The procedure DECK actually generates the deck gets it shuffled and outputs the result to the main procedure TO DECK L J MAKE L A K Q J 10 9 8 7 6 MAKE L SE L 5 4 3 2 MAKE L SE SE SE L L L L SHUFFLE 52 L 0 OUTPUT RESULT END 135 This set of procedures generates a shuffled deck of cards They could be used as they stand for any card game To test them try FT DECK PRINT RESULT It takes a few moments for the program to shuffle and print Now we must pick a specific game Perhaps the simplest card game is War War is a two player game Each player is given half the deck Each player plays the next card from
165. statement is used to assign a new shape to the current turtle The shape of a tur tle is made up of a pattern of dots on a grid The shape list tells Super LOGO how to draw the turtle pattern The turtle shape is automatically rotated to face in the direction the turtle 16 headed Drawing the turtle shape is similar to using normal turtle graphics commands to draw any shape The difference is that the commands which make up the shape list are a res tricted and simplified form of the normal turtle graphics commands The commands allow step of one pixel one square on a piece of graph paper in any of the 8 possible directions The 8 directions are up down right left and the four diagonal directions The one letter com mands that may be used in a shape list are shown below The shape list can be any length If it runs over a line boundary put a hyphen at the end of the line then continue in column 1 of the next line The turtle shape drawing pen complements the affected pixels That is the complement of a dot present is no dot present and vice versa This allows a turtle to pass over a picture without destroying the picture TURTLE SHAPE COMMAND MEANING F step forward one pixel if the pen is down complement the pixel B step backward one pixel if the pen is down complement the pixel R rotate right by 45 degrees L rotate left by 45 degrees U pick up the turtle shape pen this pen is always assumed down at the start of a shap
166. t of statements is executed otherwise it is skipped 168 IFFALSE list of stmts MAKE var expr or MAKE var expr NOTRACE NOWRAP OUTPUT expr PRINT expr procname arglist If the value of the previous TEST statement is FALSE the list of statements is executed otherwise it is skipped The value of the expression is assigned to the variable The value may be a number word or list This turns off trace mode and causes normal execution to resume Normally the screen is in wrap mode That is a turtle which runs off the screen will come back on the opposite edge Execution of the NOWRAP statement takes the screen out of wrap mode If a turtle then runs off the screen the program will terminate with an OUT OF BOUNDS error message The expression value can be a number or word or list The value is saved as the function result then control is returned to the calling procedure in the same manner as via the STOP statement The calling procedure can use the saved value via the RESULT function If the screen is in FULLTEXT mode then PRINT acts exactly like TEXT as described below Otherwise the expression value is displayed at the turtle location The turtle 16 not moved The value may be a number word or list Words in a list are separated by one space This is referred to as a CALL statement even though it does not contain the word CALL To CALL any proce dure just code its name followed by any argume
167. t the last word returns a word consisting of all letters in the argument word except the last letter returns if selected paddle button is not depressed or 1 if it is depressed Arg selects the right button arg 1 selects the left arg is a number from 0 to 255 this returns a one letter word consisting of the selected ASCII character returns the cosine of arg degrees returns returns the first word in the list returns a word consisting of the first letter in the argument word returns a list consisting of the word followed by all the elements in the list returns the heading 0 to 359 of the turtle with the specified identifica tion note HEADING ME gives your own direction If no turtle exists with the identification then 0 is returned returns the greatest integer less than or equal to the argument value returns if no key is depressed If a key is depressed then the value is the ASCII value of the character returns the last word in the list returns a word consisting of the last letter in the argument word returns a list consisting of the input words returns a list consisting of all the elements in the list followed by the word MAIL arg ME NEAR arg PADDLE arg PRODUCT x y QUOTIENT xy RANDOM arg READCHAR RC READLIST RL REQUEST RQ RESULT returns a number value MAIL is used to check for and receive mes sages sent via the SEND command The argument of the MAIL fun
168. t the same syntax as LOGO and the logical structures of the two languages are essentially the same Most of the programs in books on LOGO will run in Super LOGO with out change Super LOGO is not just LOGO under another name for another computer there are some differences between the two LOGO handles words and letters via a set of operations called list processing Many versions of LOGO allow the advanced user to handle nested lists but Super LOGO restricts the user to simple lists Many versions of LOGO use floating point numbers in arithmetic Super LOGO uses decimal arithmetic Both of these restrictions are imposed to allow the following very significant additions Super LOGO provides multiple turtles whereas most versions of LOGO provide only a single turtle Super LOGO thus can be used to introduce important concepts like multi programming and messages between independent procedures but still with great simplicity Consequences of multiple turtles include provision for simple animation and the potential for user created games All these are possible because in contrast to LOGO the memory requirements of Super LOGO are modest Super LOGO also provides a mode for doodling designed for children who are too young to type keywords reliably If you are just starting on computers all that sounds rather complex That s because we re just talking about it instead of doing it Let s do it 3 2 GETTING STARTED The steps below tell you how
169. ted equal at least they all look the same In the examples we have seen so far that didn t matter But often we want the different turtles to look different For instance it would be impossible to play many games if all the pieces or players looked the same So Super LOGO includes a way to change the shape of individual turtles As we shall see this gives us a bonus a way to do simple animation The shape of the turtle is changed by means of the SHAPE statement Following the word SHAPE is a list of turtle shape commands Turtle shapes are drawn using a very limited set of turtle graphic commands basically forward and back a single step right or left by 45 degrees and penup and pendown The commands in a SHAPE statement have absolutely no effect on the turtle position heading or pen state The symbols used for these commands are listed in the following table TURTLE SHAPE COMMAND EFFECT F Step forward one dot If the pen is down complement reverse the color of the dot B Step backward one dot If the pen is down complement the dot R Turn right 45 degrees L Turn left 45 degrees U Pick up the turtle shape pen This pen is always down at the start SHAPE command The turtle shape pen is com pletely independent of the standard turtle pen PU and PD commands have no effect on the turtle shape pen and U and D have no effect on the turtle pen D Put the turtle shape pen down If the turtle shape pen was up then putti
170. tes how slow to go A value of 127 1s the slowest speed value of 0 is full speed This terminates the execution of a procedure Control is returned to the calling procedure if there is one If the procedure was called from RUN mode then control returns to RUN mode If the procedure was called by a HATCH statement then the associated turtle goes out of existence The expression is evaluated to TRUE or FALSE The result can be used by the IFTRUE and IFFALSE state ments The expression value is displayed in the text window which 1s either the bottom three lines if the screen is not in FULLTEXT mode or the entire screen if it is in FULLTEXT mode If the optional semicolon is placed after the expression then no new line sequence is dis played and the cursor remains positioned after the last character displayed This statement defines the start of a Super LOGO proce dure It must start in column 1 of a line and must be the only statement on the line The procname may be any name of one or more letters The parameters in the parmlist may be 0 or more variables Each one consists of a colon 2 followed by any word of one or more letters This turns on TRACE mode When in trace mode execu tion pauses prior to each statement The statement 1s displayed and the user must press the ENTER key to procede VANISH WAIT expr WHILE expr list of stmts WRAP VANISH takes the current turtle out of existence This c
171. than equal to lt gt not equal to lt less than or equal to gt greater than or equal to For relational operators the arguments may be numbers words or lists Two lists are consid ered equal if they each contain the exact same list of words CONCATENATION OPERATOR argl arg2 argl and arg2 may be words or lists The operator combines the two arguments into one list consisting of the elements in argl followed by the elements in arg2 LITERALS C A quote 9 followed by one character is called a literal It can be used anywhere a number can be used The value of a literal is the ASCII value of the character For example is equal to 65 A literal is par ticularly useful in checking for values returned by the KEY function FUNCTIONS ABS arg returns the absolute positive value of the argument ASCII arg arg is a word this returns the number from 0 to 255 representing the first character of the word BUTFIRST list returns a list consisting of all words in the argument list except the BF list first word 177 BUTFIRST word BF word BUTLAST list BL list BUTLAST word BL word BUTTON arg CHAR arg COS arg DIFFERENCE xy FIRST list FIRST word FPUT word list HEADING arg INT arg KEY LAST list LAST word LIST ab LPUT word list 178 returns a word consisting of all letters in the argument word except the first letter returns a list consisting of all words in the argument list excep
172. the FALSE output With these useful subprocedures we can begin more interesting projects Conversion of a sen tence into pig latin illustrates some techniques There are various sets of rules for pig latin we ll use the one which requires movement of all leading consonants to the end of the word and the addition of AY to every word First we ll write a procedure which converts a single word TO PIG W MEMBER FIRST W A U IF RESULT OUTPUT WORD W AY PIG WORD BF W FIRST W OUTPUT RESULT END We use MEMBER to check if the first letter of a word is a vowel We pick the first letter FIRST W and check if it is in the list of vowels Remember that MEMBER returns TRUE or FALSE These words can be used as conditions in expressions for example IF RESULT The commands in the parentheses will be executed if MEMBER outputs TRUE but they will be skipped if MEMBER outputs FALSE Again remember that OUTPUT is like a STOP it returns to the next higher level The final OUTPUT RESULT takes the result from the lower level and passes it on 125 You should test this procedure before proceeding Try something like FT PIG TRANSLATE PRINT RESULT ANSLATETRAY Now we need a procedure which will work its way through a list picking off one word at a time passing it to PIG for transformation and replacing the original in the list with the new word This is useful in other contexts we are developing a model for transforming ever
173. the ball is close to the first paddle turtle 2 the heading of the ball is changed LT HEADING 4 HEADING 2 180 2 There is a similar change when the ball is close to the second paddle turtle 3 Notice that when the ball has moved the maximum distance it triggers a new ball before disappearing TO LAUNCHBALL HT PU PAT XXXXXXXX Y RANDOM 60 160 END TO STARTSPOT HT SH Y SX 60 SY 180 REPEAT 6 FD 10 WHILE XLOC 4 gt 7 amp YLOC 4 gt 7 FD 10 RT 180 ST FD 10 END LAUNCHBALL creates an appropriate shape for the ball and effectively picks a random start ing point by picking the heading STARTSPOT hides the ball turtle locates it at the first paddle moves it until it reaches the edge of the screen and finally turns it around and makes 1t visible 105 TARGET does the scoring First it picks a random position and creates target shape Then it watches for a close approach of the ball from below Gf the ball approaches from above it has not bounced off the second paddle If the ball turtle 4 comes close enough then a message is sent to the scorekeeper and to the ball TO TARGET SH 0 HT SX RANDOM 100 135 SY RANDOM 40 120 SHAPE URRFFFFFFFFFLLLDFFFF FLFFFFFFFFFLFFFFF ST REPEAT 100 IF NEAR 4 15 amp ABS HEADING 4 180 gt 90 SEND 6 1 SEND 4 1 VANISH END The SCOREKEEP procedure is essentially the
174. the loop WHILE PADDLE P 2 X 103 until there is change When there is change it runs through the outer loop which updates X erases the old paddle LINE 3 computes a new heading SH 45 3x X and draws a new paddle LINE 0 Remember that X can be between 0 and 31 so the heading for the paddle can be between 45 and 45 3 31 136 The procedure LINE actually draws the paddles and erases them The BK is broken into two steps so that it exactly duplicates the FD steps this insures a successful erase The second paddle is controlled by the second controller We can use TURN and LINE again TO PADDLE2 HT SX 180 SY 12 TURN 2 END Now we have to create the ball and the target TRIGGER starts a new round TO TRIGGER HT HATCH 4 BALL VANISH END The ball should come from a randomly selected point towards the first paddle The easiest way to do that is to create the ball turtle at the first paddle and to move it invisibly in the ran domly selected direction These two tasks will be carried out by the procedures LAUNCHBALL and STARTSPOT TO BALL LAUNCHBALL WHILE MAIL 5 0 STARTSPOT HATCH 5 TARGET REPEAT 45 FD 10 IF NEAR 2 lt 20 FD 10 LT HEADING 4 HEADING 2 18 2 FD 35 IF NEAR 3 lt 25 FD 10 LT HEADING 4 HEADING 3 2 FD 45 TRIGGER END 104 At the same time we create the target at a randomly selected position HATCH 5 TARGET The REPEAT loop actually moves the ball If
175. there is a mismatch one direction the two figures will appear together and if there is a mismatch the other way the motion will be unnecessarily jerky After all this talk about turtles we feel an obligation to actually draw something which looks a bit like a turtle As our next example we give a HERD of turtles 93 94 k e TURTLFE1 SHAPE LL BRRFRRFLLFRRFLLFFFFLBBBRFL FFFRFLBBBUFFFRFDFFFFFRFFF LFRBBBLFRFFFUBBBLFDFFFFFFFF LLFFLFFLLFFRBLBLLFRFRRFFFFF RFRFLFFFLFFFFFFFFLFFFLFRF END TO TURTLE2 SHAPE LL BRRFRRFLLFRRFLLFFFFRRFFUBB LLFDRRFFFLLFFUBLLFDFFRRFFFFFFF RRFFUFLLFDLLFFFRRFRRFFFLLFUB LLFFFRRFDFFFFFFF LLFFLFFLLFFRBLBLLFRFRRFFFFF RFRFLFFFLFFFFFFFFLFFFLFRF END TO CRAWL T X Y HT PU SX X SY Y RT 90 REPEAT 100 HATCH 1 REPEAT 8 HT FD2 HATCH 1 T2 REPEAT 8 HT FD 2 IF XLOC ME 230 VANISH END TO TURTLE1 ST REPEAT 10 END TO T2 HT TURTLE2 ST REPEAT 10 END TO HERD CLEAR DRAW HT MAKE I MAKE T 1 REPEAT 20 IF 1 lt 10 MAKE I 1 1 MAKE J 1 WHILE J lt l HATCH T CRAWL T J 18 MAKE T T 2 MAKE J J 1 REPEAT 900 END lt lt x lt lt lt lt lt Super LOGO offers another way to change the turtle shape which is most useful for the tion of games The command PAT is used to create
176. ticular letters in particular positions We give another possible use Well modify PERM2 so that it prints out every combination and allows the user to save any that are real words in a list which is printed out at the end One could let a child make the choices and review the list at the end or one could assign two turtles and let two players compete for find ing the most words from a set of letters We can save a lot of work by making the list of saved words a global variable we ll call it FIND Then we won t have to output it and pick it up as we move back up through the recursive stack from PERM2 We need to replace START and modify PERM2 147 FINDWORD WORD N NEW FT MAKE FINAL SIZE WORD MAKE N RESULT PERM WORD N NEW PRINT FINAL END TO PERM2 WORD SAVE PRINT WORD MAKE SAVE RC IF 5 Y MAKE FINAL SE FINAL WORD SW WORD 1 2 MAKE WORD RESULT PRINT WORD MAKE SAVE RC IF 5 Y MAKE FINAL SE FINAL WORD END You might try these examples FINDWORD REAL FINDWORD CATS As usual there are a number of ways we could make this set of procedures better The user could be prompted to push the key to save a word The current list of saved words could be searched using MEMBER as in Chapter 22 to prevent double saving of the same word which could happen if a letter occurs twice in the original word As usual we will leave such changes to you as projects 148 26 DICE
177. ting step after step by repeated use of the left arrow key The edited version of the procedure is stored in the memory in correct form and can be seen in EDIT mode Another type of editing the child may wish to do is to add on to the end of a previous proce dure There is no simple way to do exactly that but it is easy to produce the same effect Get into RUN mode and run the current version of the procedure That will draw the shape on the screen Get into DOODLE mode and give a second name Notice that the turtle is at the home position instead of at the end of the shape Start the new procedure with HOME key 2 raise the pen key 3 move to the end of the shape and lower the pen key 4 Now you are ready to proceed with completing the shape To get the whole shape while running either run the two procedures in sequence or in EDIT mode remove the END statement from the first procedure and the TO name statement from the second procedure If you do the latter you can remove all the turtle commands from HOME to PENDOWN at the start of the second procedure as well Thus far we have limited ourselves to horizontal vertical and 45 degree lines What about other angles Imagine a grid of squares with the turtle in a central one If the turtle is going to move one square forward there are only eight adjacent squares to move into Thus with a step forward of one unit the only angles which give consistent visible effects are 45 degrees 56 a
178. to be run again The program area can have any number of Super LOGO procedures it Each procedure begins with a TO statement TO statement must be the first and only statement on a line Other than that any number of statements can share a line each one is separated from the previous one by one or more spaces Each proce dure should end with an END statement The work area may contain many procedures at once It is a good idea to leave at least one blank line between procedures to improve readabil ity It is also a good idea to indent program lines to show the logical structure of the program The examples in this manual are all written in this manner When a LOAD command 16 used to read a text file into the program area the previous contents of the program area are first erased When a MERGE command is used to read a text file into the program area it is added to the end of the current lines in the program area This provides a way to combine text or procedures stored in different files TURTLE SPACE The turtle is a creature that has a visible shape a position and a heading The position is defined by X Y coordinate pair The heading is defined by an angle from 0 to 359 In general the turtle lives on the plane of the display screen By executing turtle graphics com mands you can make the turtle move about and if desired leave a trail Initially a turtle starts at the home position The home position is the approximate mid
179. to home If we want to start the turtle somewhere else we can The turtle can be moved to an arbitrary and absolute screen position by means of the SETX abbreviated SX and the SETY abbreviated SY commands The results of these two commands are absolute not relative to the current position of the turtle No line is drawn and no change in heading is made For example TO DOUBLE SETX 66 MANY 90 SETX 186 MANY 96 END The heading of the turtle also can be set to an absolute value independent of its current head ing The command is SETHEADING abbreviated SH or SETH The heading can be any thing between 0 and 359 degrees Zero degrees is straight up Try TO DOUBLE HT SX 66 MANY 96 SX 180 SH 0 MANY 96 END 37 ip Pau pa RM ELDER ew DUN duse em quem T Worm con i a p I unguem wo ae ap ye AUS geri als RE EMI 3 eee Regie E rM UE E F Al fire Ai ipt 2 TL rb T T iB e n x ee bras ye ee EI ly EUN eiit gee THe et Bira si as Bes remaining turtle instruction is HOME HOME returns the turtle to the home position the center of the screen with a heading of 0 degrees straight up The turtle is also made visible Procedures which draw circles and parts of circles arcs very useful in other projects There are some drawbacks to the CIRCLE procedure given in Chapter 5 page 27 It s hard to predict the size of the cir
180. tting a label with a triangle on the T key a label with a box on the B key and a label with a circle on the C key Of course you could use any other keys instead by renaming the procedures o0 As in DOODLE mode we want to have some way to erase mistakes The way to do this is to redraw the shape with the pencolor set to the background color We also have to pick a way for the child to control the erase One possibility is to use double presses of the same key to specify erase With a minor name change then we have the procedures TO T TO TT TO PC 1 PC 3 SH 0 HT PD FD 8 T1 150 FD 15 END END TRI 15 SH 305 FD 8 SH 0 PU ST END Returning the turtle to its original position makes this erase possible 61 Similar changes give 2 3 1 1 END END TO C TO CC PC 0 PC 3 C1 C1 END END We have not bothered to reprint the original versions of C and B which must be renamed C1 and B1 While we are at it we should allow for double keystrokes of the DOODLE mode commands One example should be sufficient TO 77 PC 3 BK 1 END We are in effect building a special language consisting of one keystroke commands Because of the low frustration tolerance of the audience that we are building the special language for 1t is especially important to make the language user proof do that we should define procedure for all the other keys on the keyboard The procedures are
181. used to print the current value of a variable MAIL 255 is a special version of the MAIL function MAIL 255 will accept messages from all other turtles Here we could use MAIL 3 just as well since turtle 3 is the only one sending messages to the scorekeeper The rollowing line WHILE MAIL 255 0 continues to check until mail is received One useful characteristic of the MAIL function is that like any decent mail system it will col lect messages Thus if several messages have collected from one or more sources the MAIL function will deliver the oldest undelivered message and keep the others for future reference A SEND 255 goes onto every turtle s list That message disappears from all lists when one turtle accepts it 101 Now that you have the whole set of procedures entered you try running the game start it run CATCHEM Just remember that this is an educational experience not pure entertainment You may discover that there is a flaw in the game If the runner is caught close to home then because the chaser is returned to home after each successful catch the runner is unable to escape and the score mounts You could fix this by moving the chaser else where if the runner is too close to home or by just incrementing the x position of the chaser by some large number say 100 after each catch One interesting variation of the game uses a turtle which obeys Newton s Laws These so called DYNATURTLES are set in
182. ut TRUE We then work our way letter by letter down the two words until we find a pair of letters which are different When we find such a pair we compare the positions of the two letters in the ASCII sequence Because the letters are in order start ing with the lower value comes first in alphabetical order If one word is shorter this proc ess returns zeros for the ASCII value which gives the right order 132 This completes the set of procedures To try it out enter some lists ALPHA DOG CAT BEE HORSE ZEBRA BEE CAT DOG HORSE ZEBRA If you added PRINT NEW as mentioned on page 131 you ll see the stages of the sort proc ess displayed on the screen ALPHA DOG ZEBRA 456 23 23 456 DOG ZEBRA The latter example shows that the procedures sort numbers as well To really try this out you might want a procedure that allows you to enter a longer list for sorting We ve already seen an example of such in Chapter 22 133 24 CARD GAMES The sequence of cards in a deck forms a list In principle we can program the rules of card games into a main procedure We may even be able to use the multitasking capabilities of Super LOGO to create multiple players with differing strategies The first task is to write a procedure which can shuffle a deck of 52 cards We ll stick to simple games ones in which suit hearts diamonds etc does not matter This will save us some typing but extension to games involving suits is possible To
183. ve REPEAT FOREVER The second new item is the KEY function The KEY function looks at the key board to see if any key has been pressed If no key has been pressed then KEY returns the value 0 Thus if at the time turtle 1 is executing the statement MAKE X KEY no key is depressed then the variable is given the value 0 If on the other hand a key is depressed then the variable X is given the ASCII value of the key So the KEY function returns either the ASCII value of the key depressed or 0 if no key is depressed The ASCII value is a number assigned to each key on the keyboard according to an industry wide conven tion In this procedure we do not have to know what the particular number is because the literal for example S automatically computes the ASCII value as well The next task for this procedure is to recognize which key has been depressed and to send a message to the appropriate turtle We have to decide what keys to use for what actions of the runner and the chaser We decided on the following key assignments move runner forward S turn runner left D turn runner right K move chaser forward J turn chaser left L turn chaser right So now we see what if any key was pressed First look at the statement IF X S SEND 2 1 98 The literal S gives the ASCII value of the argument S That is the condition X Sin combination with the previous KEY function checks to see whet
184. very time through the WHILE loop TREES is used to vary the turtle numbers for each tree drawn The deciduous forest uses the TREE1 procedure from page 82 To that we must add TO FOREST DRAW BACKGROUND 1 SX 236 REPEAT 3 SY 10 SX XLOC ME 40 HATCH 1 TREE1 20 SX XLOC ME 40 HATCH 2 TREE1 30 CLOUDS END TO CLOUD SIZE X SETHEADING 90 REPEAT SIZE 6 MAKE X RANDOM SIZE 2 PU FD 2 PD FD SIZE X PU BK SIZE X 2 SY YLOC ME 2 END 85 CLOUDS 2 5 10 5 180 CLOUD 60 5 100 5 164 CLOUD 30 5 190 5 176 CLOUD 65 END Again in this example we have created many turtles with the same numbers by hatching them recursively The two multiple tree drawings show the two ways in which multiple turtles can be created It makes no difference which way you do it unless you are going to refer to the turtle by number that case each turtle must have a unique number Notice the statement SX XLOC ME 40 This has the meaning SX XLOC ME 40 not SX XLOC ME 40 Now that you are working on complex sets of procedures you may want to Interrupt the com puter and pause at various times during execution especially when you are testing While procedures are actually running pressing the key produces a pause You can return to mode by pressing a second time or you can continue execution of the procedures by pressing any other key 86 17 NEW SHAPES FOR TURTLES All turtles are crea
185. w a new one after you ve learned the technique Now enter EDIT mode and look at NEW Insert SHAPE before the list of symbols and replace the DOODLE symbols with the appropriate turtle shape com mands Don t forget to include the hyphen at the end of the first line of commands At this point your procedure should be TO NEW SHAPE FFFFFFFLLLFFRRRR UFFRRFDF END Remember that lines which continue a SHAPE command cannot be indented To see how your shape looks run NEW and then enter commands like FD 20 and RT 90 In Super LOGO the standard turtle can be drawn in 360 positions but a turtle made with the 5 command has only 8 positions heading up down left right or in one of four diagonal positions Be sure to try the diagonal positions for example RT 45 because there will be some change shape as the turtle rotates to these positions To see why that is so return to the graph paper and follow your turtle instructions beginning along a diagonal It is a good idea to do this on graph paper before going to the computer as your turtle shapes might come apart upon rotation if they are drawn in the wrong sequence To show you that it can happen try the following We could have drawn essentially the same shape by the steps FFFFFRRUFFDLLLFFLLFF in the vertical or horizontal positions but in the diagonal positions this pattern comes apart as you can see if you follow the instructions on graph paper Now we move to a
186. while drawing a square with zero length sides Variables can be used in other positions as well Here s another example TO DESIGN LENGTH TIMES REPEAT TIMES SQUARE LENGTH RT 360 TIMES END Enter this and try running with a few different values of TIMES and LENGTH For example DESIGN 40 24 DRAW DESIGN 50 10 29 computer keeps track of the variables by the order Because the order the TO state ment for DESIGN is LENGTH TIMES the command DESIGN 40 24 causes the value 40 to be assigned to LENGTH and the value 24 to be assigned to TIMES Notice also that the name of the variable in the call of SQUARE SQUARE LENGTH need not be the same as the name in the definition of SQUARE TO SQUARE SIDE By the time the command SQUARE is reached within DESIGN the variable name LENGTH has a value for example 40 The value not the variable name is passed to SQUARE and then assigned by SQUARE to the variable SIDE Variables listed on the TO statement are local to the procedure Again we illustrate using the previous programs Enter TO DESIGN LENGTH N REPEAT N SQUARE LENGTH RT 360 N END TO SQUARE N REPEAT 4 FD N RT 99 END Here the variable N is used for two different quantities one in the main procedure DESIGN and another in the subprocedure SQUARE This causes no problems or confusion because the variables for the two procedures kept completely separate in the memory The variable
187. will let them pass 142 We still have to write the procedure CHECK TO CHECK HAND N CARD S WHILE HAND lt gt MAKE CARD FIRST HAND MAKE HAND BF HAND CARDTONUMBER CARD 0 MAKE T RESULT IF T 13 MAKE T 10 IF T 12 MAKE T 10 IF 11 MAKE T 10 IF T 14 MAKE T 11 MAKE S 1 MAKE N N T IF N gt 21 amp S 1 MAKE N N 10 OUTPUT N END CHECK takes cards one by one off the list and converts these cards to a number using CARDTONUMBER The face cards revalued to 10 and the ace is revalued to 11 and flagged The card values are totaled as they are processed MAKE N N T If the total is over 21 and the hand contains an ace then the total is reduced by 10 which corresponds to assigning the ace a value of 1 This completes the procedures for the game of blackjack and it completes our discussion of card games However it does not exhaust the possibilities We encourage you to try other simple games using the techniques illustrated in this chapter 143 25 WORD GAMES Word games provide a number of interesting possibilities for projects The key to many word games 15 a procedure for generating all combinations of a given number of letters The arrangements are generated by switching letters and then switching letters with other letters etc While it seems like this should be recursive it is not easy to come up with the recursive procedure We ll use this op
188. xecution of an END is equivalent to that of the STOP statement ELSE list of stmts This statement can appear only after an IF statement If the expression value on the IF statement is false then the list of statements after ELSE is executed Otherwise it is skipped FENCE Same effect as NOWRAP HATCH expr procname arglist Creates a new turtle The turtle will start at the same X Y position as its parent the turtle that HATCHed it and will be pointed in the same direction It will have the standard turtle shape The expression value becomes the new turtle s identification number a number from 1 to 254 The procname specifies the procedure to be executed by the new turtle The arglist is optional it specifies the arguments to be passed to the procedure The new turtle runs simultaneously with the other active turtles IF expr The expression is evaluated If the value is true non zero list of stmts the list of statements in parentheses is executed If it is false 0 then the list of statements is skipped The word THEN may be inserted after the expression if desired The IF statement may be followed by an ELSE state ment The list of statements denoted here and under ELSE IFTRUE IFFALSE REPEAT and WHILE can be zero or more statements except the TO statement There may be multiple statements per line and any number of lines may be used IFTRUE ist of stmts If the value of the previous TEST statement is TRUE the lis
189. y mem ber of a list into something related The key here is recursion METAMORPHIZE S H IF S 1 OUTPUT PIG FIRST S MAKE H RESULT METAMORPHIZE BF 5 OUTPUT SE H RESULT END This is a bit more complex than the recursion we ve used with words and lists thus far so let s look at it in some detail For the moment ignore the check for the empty list At every level the first word on the list is passed to PIG and the metamorphized result is stored in H Then the list minus the first word is passed down recursively Therefore when the list is empty every higher level has one metamorphized word in H and they are in order from first highest level to last lowest level When the lowest level is reached the empty list an empty list is output The next to lowest level combines the last word with this into a sentence This is in turn passed back up by the OUTPUT function As the computer works back up through the levels it combines the metamorphized word stored at that level with what is output from below to form a new sentence and it sends that to the next higher level Of course we must try this out Enter FT METAMORPHIZE A TRIAL SENTENCE and follow that with PRINT RESULT AAY IALTRAY ENTENCESAY The following may be obvious One could replace PIG with any other procedure which implemented a transformation rule We have here a way to metamorphize any list to another list so long as that metamorphosis is governed

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