ludus-scripts/sierp.ld

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& Example Ludus implementation of the Sierpinski triangle.
& https://en.m.wikipedia.org/wiki/L-system#Example_5:_Sierpinski_triangle
& The Sierpinski triangle drawn using an L-system
& variables : F G
& constants : + -
& start : F-G-G
& rules : (F -> F-G+F+G-F), (G -> GG)
& angle : 120°
& F and G both mean "draw forward", + means "turn left by angle", and means "turn right by angle".
& set a length for each segment
let length = 10
& set an angle for all turns, default to 1/3 for triangles
let angle = inv(3)
& define 'G' function from the grammaer
fn g! {
(0) -> fd!(length)
(n) -> {
g!(dec(n))
g!(dec(n))
}
}
& define 'F' function from the grammaer
fn f! {
(0) -> fd!(length)
(n) -> {
f!(dec(n))
rt!(angle)
g!(dec(n))
lt!(angle)
f!(dec(n))
lt!(angle)
g!(dec(n))
rt!(angle)
f!(dec(n))
}
}
& this function defines the starting pattern.
& each of the f! and g! calls expand based on the grammar at the top of this example
fn sierp! (times) -> {
f!(times)
rt!(angle)
g!(times)
rt!(angle)
g!(times)
}
& call the base function with a number of iterations
& remember, this is exponential! high numbers can freeze your browser.
sierp!(7)