Daily.Prog.213

213.hs

module Main where

import Data.List

xor :: [Char] -> Char
xor ['x',_,'x'] = '.'
xor ['.',_,'.'] = '.'
xor [_,_,_] = 'x'

transform xs = unlines $ take 25 $ iterate step xs
step xs = map xor $ map (take 3) (filter (\x -> length(x) >= 3) $ tails $ "." ++ xs ++ ".")

main :: IO ()
main = putStrLn $ transform ".................................................x................................................"