-- | /O(min(n,W))/. Lookup the value at a key in the map.
lookup :: Key -> IntMap a -> Maybe a
lookup k (IntMap m) = W.lookup (i2w k) m
lookup :: Key -> IntMap a -> Maybe a
lookup k (IntMap m) = W.lookup (i2w k) m
lookup k (IntMap m) = W.lookup (i2w k) m