Sierpinski Triangle

README.md

How to run:

ghc fractal.hs
./fractal

TODO:

• x y to row col

fractal.hs

----- constants
sizev = 44
sizeh = 51
r = sin(pi / 3)

----- primitive shape constructors
type Shape = Float -> Float -> Bool

rect :: Shape
rect = \ x y -> x > 0
             && y > 0
             && x < sizev
             && y < sizeh

triangle :: Shape
triangle = \x y -> rect x y
                && r >= x / (2 * y)
                && r >= x / (2 * (sizeh - y))

----- operations on primitives
scale :: Float -> Shape -> Shape
scale by shape = \x y -> shape (x / by) (y / by)

move :: Float -> Float -> Shape -> Shape
move dx dy shape = \x y -> shape (x - dx) (y - dy)

(|+|) :: Shape -> Shape -> Shape
(|+|) s1 s2 = \x y -> s1 x y || s2 x y

----- shape transformers

triple :: Shape -> Shape
triple shape = scale 0.5 $ 
        shape
        |+| move 0 sizeh shape
        |+| move (sizeh * r) (sizeh / 2) shape

shape = triple $ triple $ triple triangle

----- rendering
putPixel shape row col = putStr $ if (shape row col) then "█ " else ". "
putRow row = putChar '\n' >> mapM_ (putPixel shape row) [1..sizeh]
main = mapM_ putRow [1..sizev]