runhaskell gameoflife.hs

gameoflife.hs

import Control.Monad (forM_)
import Data.Function (on)
import Data.List (group,intercalate,maximumBy,nub,sort)
import Data.List.Split (chunksOf)

-- see http://clj-me.cgrand.net/2011/08/19/conways-game-of-life/

neighbours [x, y] = [[dx + x, dy + y] | dx <- [-1,0,1]
                                      , dy <- if (dx == 0) then [-1,1] else [-1,0,1]]

step cells = nub $ [loc | (loc, n) <- frequencies $ concatMap neighbours cells, cond loc n]
    where frequencies input = map (\x -> (head x, length x)) $ group $ sort input
          cond loc n = n == 3 || (n == 2 && loc `elem` cells)

fullBoard cells = chunksOf (size + 1) [[y,x] `elem` cells | x <- [0..size], y <- [0..size]]
    where n = maximum $ map head cells
          m = maximum $ map (head.tail) cells
          size = max n m

printableBoard cells = intercalate "\n" (map (intercalate " ") xo)
    where xo = map (\row -> map (\item -> if item then "O" else "X") row) $ fullBoard cells

main = do
    let board = [[1,0], [1,1], [1,2]]
        boards = take 5 $ iterate step board

    forM_ boards $ \b -> do
        putStrLn $ printableBoard b
        putStrLn ""