{-# LANGUAGE OverloadedLists #-}
{-# LANGUAGE TypeFamilies #-}
import GHC.IsList
import qualified Data.Array.Unboxed as A

instance A.IArray A.UArray e => IsList (A.UArray (Int,Int) e) where
  type Item (A.UArray (Int,Int) e) = [e]
  fromList [] = A.array ((0,0),(0,0)) []
  fromList ll@(hd:_) =
    let h = length ll
        w = length hd
    in A.array ((0,0),(h-1,w-1))
         [((i,j), x)
         | (row, i) <- zip ll [0..]
         , (x, j) <- zip row [0..]]
  toList arr =
    let ((0,0), (_h,w)) = A.bounds arr
    in chunksN w (A.elems arr)
    where
      chunksN n [] = []
      chunksN n l = let (pre, post) = splitAt n l
                    in pre : chunksN n post

main :: IO ()
main = do
  let arr :: A.UArray (Int,Int) Char
      arr = ["hello"
            ,"this "
            ,"is an"
            ,"array"]
  print arr