{-# LANGUAGE MultiParamTypeClasses, FlexibleInstances, FlexibleContexts, UndecidableInstances #-}

module CircularShifter where

import Data.List
import Data.Array.IO

class Line c where
    rotate :: c a -> c a
    rotateAll :: c a -> c (c a)

instance Line [] where
--  rotate :: [a] -> [a]
    rotate [] = []
    rotate (x:xs) = xs ++ [x]

--  rotateAll :: [a] -> [[a]]
    rotateAll xs = take (length xs) (iterate rotate xs)

class (Monad m) => CircularShifter a b c m where
    circularShift :: b (c a) -> m (b (c (c a)))

instance (Monad m) => CircularShifter a [] [] m where
    circularShift = return . map rotateAll

instance (Ix i, Monad m, Line c, MArray a (c x) m, MArray a (c (c x)) m) => CircularShifter x (a i) c m where
    circularShift v = mapArray rotateAll v