Hello, I'm trying to write code that will take a mutable 2D array and normalize it by dividing all elements by the largest element. I managed to write code to do this, but it seems overly complex. I could write something much simpler in Clean or C++. Most likely, my code is complex because I don't have any experience with mutable arrays in Haskell. I couldn't find any tutorials on the Internet. I'd be grateful for suggestions on simplifying the following code. Thanks. {-# OPTIONS_GHC -fglasgow-exts -fbreak-on-exception #-} -- normalize_ary This takes a mutable array. Determines the largest -- element in the array (max_elem) and then divides every element by -- max_elem. normalize_ary :: (Num t1, Num t, Ix t, Ix t1, MArray a e t2, Ord e, Fractional e, Enum t, Enum t1) => a (t, t1) e -> t2 () normalize_ary ary = do -- The following two commented out lines of code show my first -- attempt at determining a value for max_elem. However, this -- produces a stack overflow. -- elem_ary <- getElems ary -- let max_elem = foldl1 max elem_ary max_elem <- calc_max_2d_elem ary max_elem `seq` map_in_place_2d_arr (\x -> x / max_elem) ary map_in_place_2d_arr :: (MArray a e t, Enum t2, Enum t1, Ix t1, Ix t2) => (e -> e) -> a (t1, t2) e -> t () map_in_place_2d_arr fn arr = ret where ret = do ((i1,j1),(i2,j2)) <- getBounds arr ( mapM_ (\i -> do v <- readArray arr i writeArray arr i (fn v) ) [(i,j) | i <- [i1..i2], j <- [j1..j2]]) calc_max_2d_elem :: (Ord t, MArray a t t1, Ix t2, Ix t3, Num t3, Num t2) => a (t3, t2) t -> t1 t calc_max_2d_elem arr = do m <- readArray arr (0,0) (_,(i_max, j_max)) <- getBounds arr let calc_max_loop arr m (i,j) | j == j_max = return m | otherwise = do e <- readArray arr (i,j) let m2 = max e m m2 `seq` calc_max_loop arr m2 nxt_idx where nxt_idx | i == i_max - 1 = (0,j+1) | otherwise = (i+1,j) calc_max_loop arr m (0,0)