& Example Ludus implementation of the Dragon curve.
& https://en.m.wikipedia.org/wiki/L-system#Example_4:_Koch_curve

& A variant of the Koch curve which uses only right angles.
& variables : F
& constants : + −
& start  : F
& rules  : (F -> F+F−F−F+F)
& Here, F means "draw forward", + means "turn left 90°", and − means "turn right 90°"


let length = 10
let angle = 0.25

fn koch! {
  (0) -> fd! (length)
  (n) -> {
    koch! (dec (n))
    lt! (angle)
    koch! (dec (n))
    rt! (angle)
    koch! (dec (n))
    rt! (angle)
    koch! (dec (n))
    lt! (angle)
    koch! (dec (n))
  }
}

& koch! (3)