Turtle Roy

A Roy programming/learning environment with Turtle Graphics, as in the Logo programming language.

Try it online: turtle-roy.fly.dev/

Turtle functions

Command	Result
fd 100	moves 100 pixels forward
lt 45	turns left 45 degrees
rt 90	turns right 90 degrees
penup	lifts the pen, no trace left when moving
pendown	lowers the pen again for drawing
setshape "rocket-large"	changes the cursor. available (with and without -large): butterfly, car, fairy, formula, princess, rocket, turtle
clear	clear the paper and reset turtle to center
home	reset the turtle to center
bg "red"	change background color (red, rgb(255,0,0), #FF0000)
color "red"	change pen color (red, rgb(255,0,0), #FF0000)
width 10	use pen width of 10 pixels
text "HELLO"	draw the text "HELLO" beside the turtle
font "40px Arial"	changes to the 40px Arial font
font 100	changes to the 100px Courier font

Sound functions

Command	Result
say "wat"	speak!
play c	plays the note C
play c 500	plays the note C for 500 milliseconds (half a second)
play c*2	plays the note C2 (frequency = C * 2)
pause	pauses for a while
pause 1000	pauses for 1000 milliseconds (1 second)

Other functions

Command	Result
print "x"	print to console
login "raimo"	login as "raimo" (this is the author name in your saved work)
save "asdf"	save current work as "asdf"
open "asdf"	open saved work "asdf" (presuming you've saved with this name and current author name)
whoami	show the author name of the logged-in user (this is just saved in a cookie)
ls	list your saved works
sequence [fd 100, rt 90]	100 pixels forward, then right turn
s [fd 100, rt 90]	same as above
repeat 4 (say "hello")	says "hello" 5 times
r 4 (say "hello")	same as above
par [play c, play e]	playes notes C and E in parallel
later 500 (say "hello")	waits 500 milliseconds in the backround and says "hello"
interval 1000 (say "hello")	Says hello each second

Array / List functions

Example	Result	Description
range 1 3	[1,2,3]	range of numbers
length [1,2,3]	3	list length
empty [1]	false	is list empty
concat [1,2] [3]	[1,2,3]	concatenate lists
cons 1 [2,3]	[1,2,3]	prepend to list
head [1,2]	1	first item on list
tail [1,2,3]	[2,3]	all but first item on list
last [1,2]	2	last item on list
times 2 "yes"	["yes", "yes"]	repeat same element
sum [1,2,3]	6	sum of items on list
map (\x -> x * 2) [1,2]	[2,4]	map list items with function
filter (\x -> x ==1) [1,2]	[1]	filter list with function
zip plus [1,2] [3,4]	[4,6]	zip lists pairwise with function
scanl plus 0 [1,2,3]	[0,1,3,6]	accumulate values, output all
foldl plus 0 [1,2,3]	6	accumulate values, output last

In addition to this, you may use the full Roy programming language.

Examples

Bunch of examples available in the demo menu. Some more stuff here.

Basic Turtle commands

fd 100
lt 90
rt 45

Square

let square = repeat 4 (sequence[fd 50, lt 90])
square

Flower

let flower = repeat 36 (sequence[rt 10, square])
flower

Math

3 + 4
3 / 4
let factorial n = if n==1 then 1 else n * (factorial n - 1)
factorial 12

Strings

"apple" ++ "sauce"
"apple" + 10 (won't compile)

Lists

range 1 99
times 100 "lol"
head [1,2,3]
tail [1,2,3]
concat [1,2,3] [4,5,6]
length [1,2,3]
empty []
let reverse xs = if (empty xs) then [] else concat (reverse (tail xs)) [head xs]
reverse [1,2,3]
sum [1,2,3]
map (\x -> x * 2) [1,2,3]
filter (\x -> x > 1) [1,2,3]
foldl (\x y -> x * y) 1 [1,2,3]

Export

You can export your drawing as a series of commands in JSON format by opening your browser's developer console and typing turtle.export().

Building and running

Build (and rebuild on javascript changes)

npm install

Install mongodb

brew tap mongodb/brew
brew install mongodb-community

Run the server (node.js / express)

./runmongo&
./server

And

open http://localhost:8080

To build client-side code on every change, just

npm run watch

Credits

Thanks to Miikka "arcatan" Koskinen for creating tryroy, from where I shamelessly stole the Roy browser REPL.

Thanks to Brian McKenna for the Roy language and support.

See origins of the cursor images from src/main/webapp/images/image-sources.txt

Thanks to mLab for their free hosted MongoDB database.