StarLogo Vocabulary: Turtle and Patch Commands

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alive?
alive?-of ID-number

alive? reports true if the turtle is alive. alive?-of reports true if turtle with the
given ID-number is alive.
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bk number

Moves turtles backward by number steps.
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breed
breed-of id-number
breed-at xcor ycor img src="../images/observer.gif">

Reports the breed of the turtle.

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die

Tells turtles to die.

Example:
if pc = red [die]
(All turtles on red patches die.)
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distance x-coordinate y-coordinate
distance-nowrap x-coordinate y-coordinate

Reports the distance to the point (x-coordinate, y-coordinate)
With distance, turtles and patches use the "wrapped distance" (around the edges of the
screen) if that distance is shorter than the "onscreen distance." With distance-nowrap,
turtles and patches always use the onscreen distance.

Example:
if (distance 0 0) > 10 [setc green]
(All turtles more than 10 units from the center of the screen turn green.)
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dx
dy

dx reports the x-increment if the turtle were to take one step forward. dy reports
the y-increment if the turtle were to take one step forward. These primitives are useful
for "testing" the patch ahead of the turtle before moving.
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forward, fd number

Moves turtles forward by number steps.
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hatch procedure-list

Each turtle creates a new turtle, identical to itself, and tells the new turtle to
execute procedure-list.

Example:
hatch [lt 45] hatch [rt 45]
(Each turtle creates two new turtles, one angled to the left, one angled to the right.)
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heading
heading-of ID-number

heading reports the heading of the turtle. Heading 0 is due north, 90 is east, as so on.
heading-of reports the heading of the turtle with the given ID-number.
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home

Moves the turtle to the middle of the screen, at coordinates (0, 0).
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hideturtle, ht

Hides the turtle, so that it is invisible.
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jump number

Moves turtles forward by number units in one "big step" (in one unit of time).

This command is useful for synchronizing turtle movements. The command fd 15 takes
15 times longer to execute than fd 1, but jump 15 executes in the same time
as jump 1 or fd 1.
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left, lt number

Turns turtles left by number degrees.
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patchcolor, pc
pc-at dx dy

pc reports the color number of a patch.

pc-at reports the color of the patch (dx, dy) units away.

Example:
if pc = white [fd 20]
(All turtles on top of white patches move forward 20 steps.)
if pc = red [setpc blue]
(All red patches turn blue.)
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pendown, pd

Puts down the turtle's pen, so that the turtle draws (leaves a trail) when it moves.
The turtle draws by changing the color of the patches underneath it to its own color.
To change the color of the turtlešs pen (and the color of the turtle itself), use setc.
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pen-down?

Reports if the pen is down.
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psetbreed
psetbreed-at
psetbreed-of

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pstamp color
pstamp-at dx dy color

pstamp sets the color of all turtles in the patch to color.

pstamp-at is used by a patch to set the color of turtles in the patch (dx, dy)
units away.
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penup, pu

Lifts up the turtle's pen, so that the turtle doesn't draw when it moves. To put down
the turtle's pen, use pd (for pen down).
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psetshape number

Patch sets the shape of one of the turtles on top of it to number.
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psetshape-of turtle# number

Patch sets the shape of turtle turtle# to number.
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psetshape-at dx dy number

Patch sets the shape of all turtles on the patch dx dy away from it to number.
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right rt number

Turns turtles right by number degrees.
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scale-color color variable min max
scale-pc color variable min max
(scale patch color)

Sets the color (for each turtle for scale-color, for each patch for scale-pc)
to a shade of color proportional to its value of variable. The larger the
variable, the lighter the shade of color. If variable is greater than max,
color is close to white. If variable is less than min, the color is black.

Examples:
scale-color red age 0 50
(Colors each turtle a shade of red proportional to its value for the variable age.)
scale-color green chemical 0 50
(Colors each patch a shade of green proportional to its value for the variable chemical.)
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setcolor, setc color
setc-of ID-number color
setc-at dx dy color

setc sets turtle's color to the given color. See section 3 for discussion
of StarLogo colors.

setc-of sets the color of the turtle with the given ID-number.

setc-at is used by a turtle to set the color of turtles in the patch (dx, dy)
units away.

Example:
setc red
(Each turtle turns red.)
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setheading, seth number
(set heading)
Sets the heading of turtles to number. Heading 0 is due north, 90 is east, and so on.
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seth-of turtle# heading

Turtle sets the heading of turtle turtle#.
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setpatchcolor, setpc color
setpc-at dx dy color

setpc sets patch's color to the given color. See section 3 for discussion
of StarLogo colors.

setpc-at is used by a patch to set the color of the patch (dx, dy) units away.

Example:
setpc green
(Each patch turns green.)
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setxcor, setx number

Sets the x-coordinate of turtles to number.
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setxy number1 number2

Sets the x-coordinate of turtles to number1 and the y-coordinate of turtles to
number2.

Example:
setxy 0 0
(All turtles move to the center of the screen.)
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setycor, sety number

Sets the y-coordinate of turtles to number.
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setxy-of turtle# xcor ycor

Turtle sets the xcor and ycor of turtle turtle#.
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setx-of turtle# xcor

Turtle sets the xcor of turtle turtle#.
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sety-of turtle# ycor

Turtle sets the ycor of turtle turtle#.
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shape
shape-at
shape-of

Reports the shape of the turtle.
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showturtle, st

Makes the turtle visible. (Turtle can be hidden with the command ht.)
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sprout list

Patch creates a turtle which runs list.
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stamp color
stamp-at dx dy color

stamp sets the color of the patch under the turtle to the given color.
See section 3 for discussion of StarLogo colors.

stamp-at is used by a turtle to set the color of the patch (dx, dy) units away.
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towards x-coordinate y-coordinate
towards-nowrap x-coordinate y-coordinate

Reports the direction from the turtle towards the point (x-coordinate, y-coordinate).

If the "wrapped distance" (around the edges of the screen) is shorter than the "onscreen
distance," towards will report the direction of the wrapped path, while
towards-nowrap will report the direction of the onscreen path.
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one-of-turtles-at , old way: turtle-at x-offset y-offset

Reports the ID-number of another turtle in the patch that is x-offset away in the
x-direction and y-offset away in the y-direction. If there are several turtles in
the patch, an arbitrary (other) turtle is picked.

If used by a patch, and there are no turtles in the indicated patch, reports -1. If used by
a turtle, and there are no other turtles in the indicated patch, reports -1.
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one-of-turtles-here, old way: turtle-here

Reports the ID-number of another turtle in the same patch. If there are several turtles in
the patch, an arbitrary (other) turtle is picked.

If used by a patch, and there are no turtles in the patch, reports -1. If used by a turtle,
and there are no other turtles in the patch, reports -1.
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count-turtles-at, old way: turtles-at x-offset y-offset

Reports the number of turtles in the patch that is x-offset away in the x-direction
and y-offset away in the y-direction.
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count-turtles-here, old way: turtles-here

Reports the number of turtles in the patch.
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who

Reports the ID-number of the turtle.

Example:
if who < 50 [setc blue] (Makes 50 of the turtles blue.)
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xcor
xcor-of ID-number

xcor reports the x-coordinate of a turtle or a patch.

xcor-of reports the x-coordinate of the turtle with the given ID-number.

Example:
sety xcor
(Sets turtles' y-coordinate to equal x-coordinate, so that all turtles move to the line y=x.)
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ycor
ycor-of ID-number

ycor reports the y-coordinate of a turtle or a patch.

ycor-of reports the y-coordinate of the turtle with the given ID-number.

Example:
setpc ycor (Displays the StarLogo color table as horizontal bands.)
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