difference :: SmallBitSet -> SmallBitSet -> SmallBitSet
difference (SmallBitSet x) (SmallBitSet y) =
  SmallBitSet (x .&. complement y)
difference :: SmallBitSet -> SmallBitSet -> SmallBitSet
difference (SmallBitSet x) (SmallBitSet y) =
  SmallBitSet (x .&. complement y)
difference (SmallBitSet x) (SmallBitSet y) =
  SmallBitSet (x .&. complement y)