Background

jLogo Programming

Java

Appendices

Updates

Lastly

Appendix C (Primitive Procedures)

Introduction

jLogo's primitive procedures are core building blocks of the language. You may not use the names of of these primitive procedures for names of procedures you write.

Data Manipulation
Flow-Control Procedures
Graphics Procedures
Logical Procedures
Math Procedures
Multi-Threading
Predicates
User-Interface Procedures
Variables

Data Manipulation

Name	Input(s)	Description	Example
ARRAYTOLIST	array	Outputs a list whose members are the members of the input array.	MAKE "xxx ARRAYTOLIST :ary
BUTFIRST BF	wordOrSentence	If the input is a word, all characters except its first are output. If the input is a sentence, all words except the first are output.	BUTFIRST :WD
BUTLAST BL	wordOrSentence	If the input is a word, all characters except its last are output. If the input is a sentence, all words except the last one are output.	BUTLAST :SENT
CHAR	number	outputs a single character word that is the ASCII code corresponding to the input (an integer between 0 and 127).	CHAR 65
COUNT	array number wordOrSentence	If the input is an array, the number of members it is composed of is output. If the input is a number or a word, the number of characters in it is output. If the input is a sentence, the number of words in it is output.	COUNT :WD
FIRST	wordOrSentence	If the input is a word, its first character is output. If the input is a sentence, its first word is output.	FIRST :WD
FPUT	thing list	Outputs a list equal to its second input with one extra member, thing, at the beginning. If the second input is a word, then the first input must be a one-letter word, and FPUT is equivalent to WORD.
ITEM	number wordOrSentence	Outputs the number-th element of its second input. If its second input is a word, it outputs a word consisting on the number-th character. If its second input is a sentence, it outputs the number-th word of it.	ITEM 2 :SENT
LAST	wordOrSentence	If the input is a word, its last character is output. If the input is a sentence, its last word is output.	LAST :WD
LIST	thing1 thing2	Outputs a list whose members are its inputs, which can be any jLogo datum (arrays, lists, and words).
LISTTOARRAY	list	Outputs an array whose elements are the elements of the input list.
LOWERCASE	word	Outputs a copy of the input word, but with all uppercase letters changed to the corresponding lowercase letters.
LPUT	thing list	Outputs a list equal to its second input with one extra member, the first input, at the end. If the second input is a word, then the first input must be a one-letter word, and the output:
READLIST		Get a line of text input from the user (in the CommandCenter) and output it as a sentence.	MAKE "sent READLIST
READWORD		Get a line of text input from the user (in the CommandCenter) and output it as a word.	MAKE "yesNo READWORD
SENTENCE SE	wordOrSentence wordOrSentence	Outputs a sentence consisting of its first input concatenated with its second input.	SENTENCE "word :sent
THING	name	Outputs the value in its input, a global variable named name. Dots name (":NAME") can be thought of as an abbreviation for THING "NAME. But, the real need for THING is when the names of global variables are constructed dynamically.	THING :curSequence
UPPERCASE	word	Outputs a copy of the input word, but with all lowercase letters changed to the corresponding uppercase letters.
WORD	word1 word2	Outputs a word consisting of its first input concatenated with its second input.	WORD "$ :word

Flow-Control Procedures

Name	Input(s)	Description	Example
EVALUATE EVAL	operation	The input operator, which must be a word or list, is performed and the output is the output of EVALUATE. This provides a mechanism for a program to dynamically construct an operation.
IF	trueFalse instructionList	If the trueFalse input is true, the instructionList input is performed. If trueFalse is false, nothing is done.	IF LESS? MOUSEX 0 [ ... ]
IFELSE	trueFalse instructionList1 instructionList2	If the trueFalse input is true, the instructionList1 input is performed. If trueFalse is false, instructionList2 is performed.	IFELSE PENDOWN? [ ... ] [ ... ]
OUTPUT	value	The current invocation of the procedure in which OUTPUT exists terminates and the value it outputs is value.	OUTPUT RANDOM 16
REPCOUNT		Outputs the current value of the variable controlling iteration in the REPEAT command in which it is invoked.	REPEAT 20 [PRINTLN REPCOUNT]
REPEAT	count instructionList	The instructionList input is performed the number of times specified by the count input.	REPEAT 4 [FD 100 RT 90]
REPEAT	rangeSentence instructionList	The instructionList input is performed while REPCOUNT is within the range of the first and second values in rangeSentence; REPCOUNT starts at the first element in rangeSentence and moves toward the second element in rangeSentence in increments as specified by the third element in rangeSentence.	REPEAT [-2 2 .5] [PRINTLN REPCOUNT]
RUN	sentence	Execute the sentence as if it were typed into the CommandCenter - instructions as data.	RUN :cmdsSent
STOP		The current invocation of the procedure in which STOP exists terminates.	IF EQUAL? :inp 0 [STOP]
WAIT	number	Performing instructions is suspended for the number of milliseconds (1/1000s of a second).	WAIT 1000

Graphics Procedures

Name

Input(s)

Description

Example

BACK
BK

number

Moves the turtle backward, i.e., exactly opposite to the direction that it's facing, by the specified number of turtle steps.

BACK 150

CANVASHEIGHT

Outputs the current height of the GraphicsCanvas in turtle steps.

CANVASWIDTH

Outputs the current width of the GraphicsCanvas in turtle steps.

CG
CLEAN

Erases everything that the turtle has drawn on the GraphicsCanvas. The turtle's state (position, heading, pen color, etc...) is not changed.

COLORSUNDER

Outputs a list of the colors under the turtle's image, one element for each unique color.

COLORUNDER

The color under the center of the turtle, the tip of the pen, is output.

PRINTLN COLORUNDER

FILL

Whatever color is under the turtle is changed to the turtle's color, and this process is repeated in an outward manner for all pixels that are neighbors and match the original color.

FILL

FORWARD
FD

number

Moves the turtle forward, in the direction it is facing, by the specified number of turtle steps.

FORWARD 100

GETPIXELS

rectList

Outputs an array of pixel values specified by the input rectangleList, a List of four numbers. The first number is the left-most X edge of the rectangle, the second number is the top Y edge of the rectangle, the third number is the width of the rectangle, and the fourth number is the height of the rectangle, e.g., (sentence :leftX :topY :width :height).

MAKE "ary
GETPIXELS :x :y :wd :ht

HEADING

Outputs the turtle's heading in degrees.

HIDETURTLE
HT

Hides the turtle, makes it invisible.

HOME

Moves the turtle to the center of the GraphicsCanvas, i.e., coordinates 0,0.

LABEL

wordOrSentence

The text representing LABEL's input is drawn in the GraphicsCanvas.

LABEL "START

LEFT
LT

number

Turns the turtle counterclockwise by the specified angle measured by a number of degrees (1/360 of a circle).

LEFT 180

LOADPICTURE
LOADPICT

word

Load the .BMP picture specified by word into the background of TG's GraphicsCanvas.

LOADPICT "natalie

LOADSHAPE

word number

Load the .BMP picture named word into TG's turtle shapes; the picture is given the identifier number. Number must be in the range of 16 through 31. The SETSHAPE command can then be used to set the turtle's image to the picture.

LOADSHAPE "bat 16

PENCOLOR

Outputs the color number of the turtle's pen.

MAKE "savCol PENCOLOR

PENDOWN
PD

Puts the turtle's pen down so that it leaves a trace when it moves.

PENSIZE

Outputs the size of the turtle's pen, its width in turtleSteps.

MAKE "savSiz PENSIZE

PENUP
PU

Lifts the turtle's pen up so that it leaves no trace when it moves.

POS

Outputs the current coordinates of the turtle as a sentence. The X coordinate is the FIRST of the sentence; the Y coordinate is the LAST of the sentence.

MAKE "point POS

RIGHT
RT

number

Turns the turtle clockwise by the specified angle, measured in degrees (1/360 of a circle).

RT 90

SETBACKGROUND
SETBG

number

Sets the color of the background of the GraphicsCanvas. Color is expressed as a number.

Number	Color	Number	Color
0	black	8	brown
1	blue	9	tan
2	green	10	forest
3	cyan	11	aqua
4	red	12	salmon
5	magenta	13	violet
6	yellow	14	orange
7	white	15	grey

SETBACKGROUND 1

SETHEADING
SETH

number

Turns the turtle to a new absolute heading. The input, number, is the heading (in degrees) clockwise from the positive Y axis, i.e.,
0 is due North (up),
90 is due East (right),
180 is due South (down), and
270 is due West (left).

SETH 90

SETLABELHEIGHT
SETLH

number

The height of characters drawn with the LABEL procedure is set to the input.

Number	CharHeight	CharWidth
12	9	7
14	10	8
16	12	9
18	14	10
24	18	14
32	22	18

SETLABELHEIGHT 32

SETPENCOLOR
SETPC

number

Sets the turtle's color - the color of its pen. Color is expressed as a number.

Number	Color	Number	Color
0	black	8	brown
1	blue	9	tan
2	green	10	forest
3	cyan	11	aqua
4	red	12	salmon
5	magenta	13	violet
6	yellow	14	orange
7	white	15	grey

SETPC 10

SETPENSIZE
SETPS

number

Sets the width of the turtle's pen, which determines the thickness of the trace it leaves, the line it draws.

SETPS 5

SETPIXELS

rectList,
pixelArray

Paints the values of pixels in pixelArray onto the area of the GraphicsCanvas specified by rectList. Pixel values are color numbers. A rectList has the form [leftX, topY, width, height].

SETPOS

sentence

Moves the turtle to an absolute position, specified by a sentence containing two numbers. The two numbers are (FIRST) a new horizontal (X) coordinate and (LAST) a new vertical (Y) coordinate.

SETPOS [100 100]

SETSHAPE
SETSH

number

Sets the turtle's shape to a specified shape. Shape is expressed as a number. The built-in shapes are:

Number	Shape	Number	Shape
0	Turtle	3	Box
1	Arrow	4	Cross
2	Ball	5	Triangle

SETSHAPE 2

SETSHAPE
SETSH

number-sentence

Sets the turtle's shape to a specified shape and size. The first number in the sentence is the shape number (see SETSHAPE number) and subsequent numbers specify a preferred size, which is shape dependent.

SETSHAPE [3 100 10]

SETX

number

Moves the turtle horizontally to the specified absolute window position.

SETX 100

SETXY

number1
number2

Moves the turtle to an absolute position, specified as two numbers: the new horizontal (X) and vertical (Y) coordinates.

SETXY 50 -30

SETY

number

Moves the turtle vertically to the specified absolute window position.

SETY 100

SHAPEHEIGHT

Outputs the height of the turtle's shape in pixels, the image for its current heading.

SHAPEPIXELS

Outputs a list containing two elements. The first is the number of pixels in each row of the turtle's shape. The second is an array containing all of the pixels that make up the shape's image.

SHAPEWIDTH

Outputs the width of the turtle's shape in pixels, the image for its current heading.

SHOWTURTLE
ST

Makes the turtle visible.

STAMP

Paint the turtle's image onto the graphics canvas.

TOWARDS

twoNumSent

Outputs a number, the heading at which the turtle should be facing so that it would point from its current position to the position given as an input - a sentence consisting of two numbers.

SETH TOWARDS [0 0]

XCOR

Outputs the turtle's X-coordinate.

YCOR

Outputs the turtle's Y-coordinate.

Logical Procedures

Name

Input(s)

Description

Example

AND

trueFalse1 trueFalse2

Outputs true if trueFalse1 AND trueFalse2 are true, false otherwise. td> trueFalse1

trueFalse2	Output
true	true	true
true	false	false
false	true	false
false	false	false

AND true true

NOT

trueFalse

Outputs false if trueFalse is true, else true if trueFalse is false - the opposite trueFalse value.

NOT true

trueFalse1 trueFalse2

Outputs true if trueFalse1 OR trueFalse2 is true, false otherwise.

trueFalse1	trueFalse2	Output
true	true	true
true	false	true
false	true	true
false	false	false

OR false false

Math Procedures

Name	Input(s)	Description	Example
ABS	number	Outputs the absolute value of number	ABS -15
ARCTAN	number	Outputs the arc tangent of number in degrees.
ASCII	character	Outputs the integer (between 0 and 127) that represents the character in the ASCII code.	ASCII "A
ASHIFT	num1 num2	Outputs num1 arithmetic-shifted to the left by num2 bits. If num2 is negative, the shift is to the right with sign extension. The inputs must be integers.
BITAND	num1 num2	Outputs the bitwise AND of its inputs, which must be integers.
BITNOT	number	Outputs the bitwise NOT of its input, which must be an integer.
BITOR	num1 num2	Outputs the bitwise OR of its inputs, which must be integers.
BITXOR	num1 num2	Outputs the bitwise exclusive OR of its inputs, which must be integers.
CEIL	number	Outputs the smallest integer (closest to negative infinity) that is not less than number.	CEIL 44.223
COS	number	Outputs the trigonometric cosine of number which is in degrees	COS 45
DIFFERENCE	number1 number2	Outputs the result of subtracting number2 from number1	DIFFERENCE 15 7
FLOOR	number	Outputs the largest integer (closest to positive infinity) that is not greater than number.	FLOOR 12.875
INT	number	Outputs number with its fractional part removed.
LSHIFT	num1 num2	Outputs num1 shifted to the left by num2 bits. If num2 is negative, the shift is to the right with zero fill. The inputs must be integers.
LOG	number	Outputs the natural logarithm of the input number.
MINUS	number	Outputs the negative of number	MINUS 122
POWER POW	num1 num2	Outputs num1 to the num2 power.
PRODUCT	number1 number2	Outputs the result of multiplying number1 by number2	PRODUCT 10 6
QUOTIENT	number1 number2	Outputs the result of dividing number1 by number2	QUOTIENT 12 4
RANDOM	number	Outputs some integer greater-than or equal-to zero AND less-than number	RANDOM 100
REMAINDER	number1 number2	Outputs the remainder left after dividing number1 by number2	REMAINDER 17 3
ROUND	number	Outputs the closest integer to number	ROUND 22.45
SIN	number	Outputs the trigonometric sine of number which is in degrees	SIN 45
SQRT	number	Outputs the square root of number	SQRT 16
SUM	number1 number2	Outputs the result of adding number1 and number2	SUM 3 4
TAN	number	Outputs the trigonometric tangent of number which is in degrees
TIME		Outputs the current time in milliseconds since January 1, 1970. TIME can be used to measure how long it takes to do something.

Multi-Threading Support

Name	Input(s)	Description	Example
ASK	name [operation]	The turtle named name is passed an operation (an operator and its inputs if any) which it interprets and outputs the result to the asking turtle.	ASK "otherTurtle [POS]
NEWTURTLE	name	Creates a new turtle with the specified name. The new turtle appears in the home position with its pen down.	NEWTURTLE "t2
TELL	name instructionList	Tells the turtle named name to perform the instructionList.	TELL "t2 [ FD 10 ]
WHO		Outputs the name of the current turtle.

Predicates

Name	Input(s)	Description	Example
ARRAY? ARRAYP	thing	Outputs true if the input thing is an array, else outputs false.
EMPTYP EMPTY?	wordOrSentence	Outputs true if its input is a word that has no characters in it, otherwise false. Outputs true if its input is a sentence that has no words in it, otherwise false.	EMPTY? :SENT
EQUAL? EQUALP	value1 value2	If value1 is equal to value2, EQUAL? outputs true. If not, false is output.	EQUAL? MOUSEX 0
GREATER? GREATERP	value1 value2	If value1 is greater than value2, GREATER? outputs true. If not, false is output.	GREATER? MOUSEX 0
LESS? LESSP	value1 value2	If value1 is less than value2, EQUAL? outputs true. If not, false is output.	LESS? MOUSEX 0
LIST? LISTP	thing	Outputs true if the input thing is a list; otherwise false is output.
MEMBER? MEMBERP	characterOrWord wordOrSentence	Outputs true if its first input is in its second input, otherwise it outputs false.	MEMBER? "e :WD
NUMBER? NUMBERP	thing	Outputs true it the input thing is a number, else outputs false.
PENDOWN?		Outputs true if the turtle's pen is in the down position, otherwise false.
WORD? WORDP	thing	Outputs true it the input thing is a word (which includes numbers and boolean values). Otherwise outputs false, e.g., if thing is an array or a list.

User-Interface Procedures

Name

Input(s)

Description

Example

KEYPRESSED

keyNumber

When a keyboard key is pressed, TG receives an event. If the key is one that TG is interested in, a user-defined procedure with the name KEYPRESSED (expecting one input) is invoked if it has been defined.

Key Number	Keyboard Key
10	Enter
32	Space
48 - 57	0 - 9
65 - 90	A - Z
97 - 122	a - z
128	Down-Arrow
129	Left-Arrow
130	Right-Arrow
131	Up-Arrow

TO keyPressed :num
PRINTLN WORD "key= :num
END

LOADCLIP

word
clipNumber

Reads in the .wav (waveform) audio file named word and associates it with clipNumber. This clip can then be played with the PLAYCLIP command. ClipNumber must be in the range 16 - 31.

LOADCLIP "meow.wav 16

MOUSECLICKED

When a mouseClicked Event is received by the jLogo interpreter, it performs a user-defined procedure with the name MOUSECLICKED, if one has been defined.

MOUSEMOVED

When a mouseMoved Event is received by TG, it performs a user-defined procedure named mouseMoved, if one has been defined. mouseMoved Events only happen when the GraphicsCanvas is active, i.e., the mouse was previously clicked on it.

to mouseMoved
   ...
   end

MOUSEPOS

Outputs the X and Y coordinates where the mouse was when it was last clicked or moved as a two member sentence.

MOUSEX

Outputs the X-coordinate where the mouse was when it was clicked.

MOUSEY

Outputs the Y-coordinate where the mouse was when it was clicked.

PLAYCLIP

clipNumber

A WAV (waveform) audio clip is played.

Number	Audio Clip
1	Cat Meow
2	Computer Beeps
3	Dog Bark
4	Fairy Dust
5	Horse
6	Laser
7	Pop
8	Zoop

PLAYCLIP 2

PLAYNOTE

noteNumber
length

A MIDI note number is played for length seconds. In this scheme, middle C is note number 60 with all other notes relative to this.


                           Note Numbers
 Octave |  C  C#    D  D#    E    F  F#    G  G#    A  A#    B
 -------+--------+--------+----+--------+--------+--------+---
   -1   |  0   1 |  2   3 |  4 |  5   6 |  7   8 |  9  10 | 11
    0   | 12  13 | 14  15 | 16 | 17  18 | 19  20 | 21  22 | 23
    1   | 24  25 | 26  27 | 28 | 29  30 | 31  32 | 33  34 | 35
    2   | 36  37 | 38  39 | 40 | 41  42 | 43  44 | 45  46 | 47
    3   | 48  49 | 50  51 | 52 | 53  54 | 55  56 | 57  58 | 59
    4   | 60  61 | 62  63 | 64 | 65  66 | 67  68 | 69  70 | 71
    5   | 72  73 | 74  75 | 76 | 77  78 | 79  80 | 81  82 | 83
    6   | 84  85 | 86  87 | 88 | 89  90 | 91  92 | 93  94 | 95
    7   | 96  97 | 98  99 |100 |101 102 |103 104 |105 106 |107
    8   |108 109 |110 111 |112 |113 114 |115 116 |117 118 |119
    9   |120 121 |122 123 |124 |125 126 |127

The absolute octave number designations shown here are based on Middle C = C4.

PLAYNOTE 60 2

PRINT
TYPE

thing

Displays thing in the terminal window.

PRINT MOUSEX

PR
PRINTLN

thing

Displays thing in the terminal window. The line is then finished off by moving the cursor to the start of the next line.

PRINTLN HEADING

Variables

Name	Input(s)	Description	Example
ARRAY	size	Outputs an array of size members, each of which is initially an empty sentence. Size must be a positive integer.	MAKE "ARY ARRAY 5
GLOBAL	name	Declares a global variable named name. The variable can be referenced anywhere in the program's text following this command. The variable has no initial contents.	GLOBAL "var
LOCAL	name	Declares a local variable named name. The variable is local to the procedure it is in. The variable has no initial contents.	LOCAL "var
LOCALMAKE	word value	Creates a variable with access limited to the procedure containing the LOCALMAKE command. The variable's name is word. The contents of the variable is set to value.	LOCALMAKE "rightX sum :leftX :wd
MAKE	name value	Creates a variable named name if it doesn't already exist. The contents of the variable is set to value.	MAKE "WHITE 7
THING	name	Outputs the value in its input, a global variable named name. ":NAME" is an abbreviation for THING "NAME. But, its real need is when the names of global variables are constructed dynamically.	THING :curSequence
SETITEM	index array value	Replaces the indexth member of array with value.	SETITEM 2 :nums "two

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