{-# LANGUAGE FlexibleContexts #-} -- only to satisfy the circularShift type spec being there

module CircularShift ( 
    circularShift
) where

import Data.Array.IO

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

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

-- type generated by GHCi
circularShift :: (Ix i, MArray a [e] m, MArray a [[e]] m) => a i [e] -> m (a i [[e]])
circularShift = mapArray rotateAll