cellular_automata.hs

module Main where

import System.Random
import Control.Monad.State.Strict

main = do
    putStrLn $ evalState ((loop 100) =<< genCell 100) (mkStdGen 1)

newtype Cell = Cell { unwrapCell :: [Bool] }

genBool :: State StdGen Bool
genBool = state random

genBoolList :: Int -> State StdGen [Bool]
genBoolList n = replicateM n genBool

genCell :: Int -> State StdGen Cell
genCell n = Cell <$> genBoolList n

appendEdge :: [Bool] -> [Bool] -> [Bool]
appendEdge [fst, lst] c = fst : c ++ [lst]

appendedCell :: Cell -> State StdGen [Bool]
appendedCell cell = (\t -> appendEdge t (unwrapCell cell)) <$> replicateM 2 genBool

nextStateList :: [Bool] -> [Bool]
nextStateList (a:b:c:xs) = (nextStateBool a b c) : (nextStateList (b:c:xs))
nextStateList _ = []

nextStateBool :: Bool -> Bool -> Bool -> Bool
nextStateBool False False False = False
nextStateBool False False True  = False
nextStateBool False True  False = False
nextStateBool False True  True  = True
nextStateBool True  False False = True
nextStateBool True  False True  = True
nextStateBool True  True  False = False
nextStateBool True  True  True  = True

nextState :: Cell -> State StdGen Cell
nextState cell = ((\t -> Cell t) . nextStateList) <$> appendedCell cell

loop :: Int -> Cell -> State StdGen String
loop 0 cell = pure $ show cell
loop n cell = (\t -> (show cell) ++ "\n" ++ t) <$> ((loop (n - 1)) =<< nextState cell)

instance Show Cell where
    show cell = map (\t -> if t then '+' else '-') $ unwrapCell cell