Luxor provides some basic "turtle graphics" functions. Functions to control the turtle begin (somewhat unusually) with a capital letter: Forward, Turn, Circle, Orientation, Towards, Rectangle, Pendown, Penup, Pencolor, Penwidth, and Reposition, and so on, and angles are specified in degrees rather than radians.
using Luxor, Colors Drawing(600, 400, "../assets/figures/turtles.png") origin() background("midnightblue") 🐢 = Turtle() # you can type the turtle emoji with \:turtle: Pencolor(🐢, "cyan") Penwidth(🐢, 1.5) n = 5 for i in 1:400 global n Forward(🐢, n) Turn(🐢, 89.5) HueShift(🐢) n += 0.75 end fontsize(20) Message(🐢, "finished") finish()
|List of words the turtle knows||Action|
|More forward by d units|
|Increase the turtle's rotation by n degrees|
|Draw filled circle centered at current pos|
|Shift the Hue of the turtle's pen color by n|
|Set the turtle's orientation to n degrees|
|Set opacity to random value|
|Set the Red, Green, and Blue values|
|Set the width of the line to n|
|Move turtle to the value stored on the stack|
|Save the turtle's position on the stack|
|Randomize the saturation of the current color|
|Draw filled rectangle centered at current pos|
|Place turtle at new position|
|Rotate turtle to face towards a point|
The turtle commands expect a reference to a turtle as the first argument (it doesn't have to be a turtle emoji!), and you can have any number of turtles active at a time.
quantity = 9 turtles = [Turtle(O, true, 2π * rand(), (rand(), rand(), 0.5)...) for i in 1:quantity] Reposition.(turtles, first.(collect(Tiler(800, 800, 3, 3)))) n = 10 Penwidth.(turtles, 0.5) for i in 1:300 global n Forward.(turtles, n) HueShift.(turtles) Turn.(turtles, [60.1, 89.5, 110, 119.9, 120.1, 135.1, 145.1, 176, 190]) n += 0.5 end finish() # hide
A turtle graphics approach lends itself well to recursive programming. This short recursive function draws a Hilbert curve.
function hilbert(t::Turtle, level, angle, lengthstep) level == 0 && return HueShift(t, 0.1) Turn(t, angle) hilbert(t, level-1, -angle, lengthstep) Forward(t, lengthstep) Turn(t, -angle) hilbert(t, level-1, angle, lengthstep) Forward(t, lengthstep) hilbert(t, level-1, angle, lengthstep) Turn(t, -angle) Forward(t, lengthstep) hilbert(t, level-1, -angle, lengthstep) Turn(t, angle) end @draw begin background("black") setline(2) setlinecap("round") hilbert(Turtle(first(BoundingBox()) + (12, 12), true, 0, (1, 0, 0)), 6, # level 90, # turn angle, in degrees 6 # steplength ) end