L-system

pythagoras.hs

{-# LANGUAGE MultiWayIf #-}

data Variables = Zero | One | LB | RB deriving (Show, Eq)

-- LB and RB symbolises left and right brackets, i.e. [, ]
pythagoras = concatMap (\c -> if
                    | c ==  Zero -> One : [LB, Zero, RB, Zero]
                    | c == One -> One : [One]
                    | c == LB -> [LB]
                    | c == RB -> [RB])


main :: IO ()
main = do
  putStrLn "First generation:"
  print $ iterate pythagoras [Zero] !! 1
  putStrLn "Second generation:"
  print $ iterate pythagoras [Zero] !! 2
  putStrLn "Third generation:"
  print $ iterate pythagoras [Zero] !! 3