TURTLE.md

Turtles App API

Basics

• At the beginning, only one turtle whose name is :trinity (don't omit ':' (colon), it is a Clojure keyword) will show up at the home position (center). This turtle, :trinity, can move forward/backward, change head angle clockwise/counterclockwise.

• Turtles can be added with a name.

• Each turtle can move independently giving a command with the name. If only :trinity is there, you don't need to give the name to commands.

Movement

All parameters to forward, backward, right, and left commands are relative to the current position or angle.

command	description
(forward len) (forward n len)	moves the turtle forward by len.
(backward len) (backward n len)	moves the turtle backward by len.
(right a) (right n a)	changes the turtle head by degrees clockwise.
(left a) (left n a)	changes the turtle head by degrees counterclockwise.
(undo) (undo n)	undos the last line and back the turtle.
(home) (home n)	moves the turtle back to the home position.
(home-all)	moves all turtles back to the home position.

usage examples

(forward 30)         ;; :trinity moves only when :trinity is there
(forward :neo 40)    ;; :neo moves

(backward 35)        ;; :trinity moves only when :trinity is there
(backward :neo 100)  ;; :neo moves

(right 45)           ;; :trinity tilts her head 45 degrees clockwise only when :trinity is there
(right :neo 90)      ;; :neo tilts his head 90 degrees clockwise

(left 30)            ;; :trinity tilts her head 30 degrees counterclockwise only when :trinity is there
(left :neo 135)      ;; :neo tilts his head 135 degrees counterclockwise

(undo)               ;; :trinity's last line will be removed only when :trinity is there
(undo :neo)          ;; :neo's last line will be removed

(home)               ;; moves :trinity back to the home position, center only when :trinity is there
(home :neo)          ;; moves :neo back to the home position, center

(home-all)           ;; moves all turtles back to the home position

Turtle

command	description
(add-turtle n)	adds a turtle with its name.
(turtle-names)	returns all turtle names.
(state) (state n)	returns a current state of the turtle.
(state-all)	returns current states of all turtles.

usage examples

(add-turtle :neo)    ;; adds a turtle whose name is :neo

(turtle-names)       ;; returns all turtle names

(state)              ;; returns :trinity's current state only when :trinity is there

(state :neo)         ;; returns :neo's current state

(state-all)          ;; returns all turtles' current states

The state command shows the absolute values not like relative values used in forward, backward, right and left. For example, {:trinity {:x 0, :y 0, :angle 90, :color [30 30 30]}}.

Absolute dimensions and angles are setup as in below:

x and y in absolute values

position	x and y values
home	both x and y are zero. (x, y) = (0, 0)
rightmost	x is 240, y is any. (x, y) = (240, y)
leftmost	x is -240, y is any. (x, y) = (-240, y)
top	x is any, y is 150. (x, y) = (x, 150)
bottom	x is any, y is -150. (x, y) = (x, -150)

angle in absolute degrees

head	angle
right	0
up	90
left	180
down	270

Clean up

command	description
(clean) (clean n)	cleans all lines belong to the turtle.
(clean-all)	cleans all lines of all turtles.

usage examples

(clean)              ;; cleans all of :trinity's lines only when :trinity is there
(clean :neo)         ;; cleans all of :neo's lines

(clean-all)          ;; cleans all turtles all lines

Initialize

command	description
(init)	makes back to the starting state.

usage examples

(init)               ;; makes back to the starting state, only :trinity is in home position

Samples

How to Walk Turtles has more examples as well as function study materials.

License

ClojureBridge Curriculum by ClojureBridge is licensed under a Creative Commons Attribution 4.0 International License.