HashMap attempt in Haskell

gistfile1.hs

import Data.Array
import Data.Maybe
import Data.Bits

type Hash = Integer
type HashMap k v = Array Hash [(k,v)]

hmCreate :: (Eq k, Show k) => HashMap k v -> k -> v -> HashMap k v
hmCreate hm k v = hm // [(hmHash hm k, after)]
  where
    before = hm ! hmHash hm k
    after = maybe ((k,v) : before) (const before) $ hmRead hm k

hmRead :: (Eq k, Show k) => HashMap k v -> k -> Maybe v
hmRead hm k = lookup k $ hm ! hmHash hm k

hmUpdate :: (Eq k, Show k) => HashMap k v -> k -> v -> HashMap k v
hmUpdate hm k v = hm // [(hmHash hm k, after)]
  where
    before = hm ! hmHash hm k
    after = maybe before go $ hmRead hm k
    go x = (k,v) : filter ((/= k) . fst) before

hmRemove:: (Eq k, Show k) => HashMap k v -> k -> HashMap k v
hmRemove hm k = hm // [(hmHash hm k, after)]
  where
    before = hm ! hmHash hm k
    after = filter ((/= k) . fst) before

hmInsert :: (Eq k, Show k) => HashMap k v -> k -> v -> HashMap k v
hmInsert hm k v = hmCreate (hmRemove hm k) k v

hmHash :: Show k => HashMap k v -> k -> Hash
hmHash hm k = foldl (\h c -> 33 * h `xor` (toInteger . fromEnum) c) 5381 (show k) `mod` mb
  where
    (lb,mb) = bounds hm

main = do
  let x = array (0,100) [(i, []) | i <- [1..100]]
  print $ hmRead (hmInsert x "hello" "world") "hello"