differenceM :: IntMap a -> IntMap b -> IntMap a
differenceM (IntMap m1) (IntMap m2) = IntMap (W.differenceM m1 m2)
differenceM :: IntMap a -> IntMap b -> IntMap a
differenceM (IntMap m1) (IntMap m2) = IntMap (W.differenceM m1 m2)
differenceM (IntMap m1) (IntMap m2) = IntMap (W.differenceM m1 m2)