Sierpinski’s classic fractal.
> import Diagrams.Backend.SVG.CmdLine> {-# LANGUAGE NoMonomorphismRestriction #-}
> import Diagrams.Prelude#### Brent’s Original Code > – sierpinski 1 = triangle 1 > – sierpinski n = s > – === > – (s ||| s) # centerX > – where s = sierpinski (n-1)
#### Code to change color at each level ##### (Technically this is the complement of the Sierpinski triangle) > import Diagrams.Prelude > import Data.Colour.Palette.BrewerSet > > clrs :: [Colour Double] > clrs = brewerSet Purples 9 > > sierpinski :: Int -> [Colour Double] -> Diagram B > sierpinski n c = go n <> triangle (2^n) # fc (clrs !! 0) # lw none > where > clrs = if null c then repeat black else cycle c > go n > | n == 1 = t1 # fc (clrs !! 1) > | otherwise = appends tri (zip vecs (replicate 3 sierp)) > where > tri = scale (2 ^ (n-1)) $ t1 # fc (clrs !! (n+1)) > vecs = [unitY, (rotateBy (-1/12) unitX), (rotateBy (1/12) unit_X)] > sierp = go (n-1) > t1 = triangle 1 # reflectY > > example = sierpinski 7 clrs # lw none # center # frame 2
> main = mainWith (example :: Diagram B)