containers: symmetricDifference for Set and HashSet

Would it make sense to add a function like the following to containers: symmetricDifference :: Set a -> Set a -> (Set a, Set a, Set a) symmetricDifference a b = (a \\ b, a `intersection` b, b \\ a) with the idea that this can be implemented more efficiently as a primitive than the above specification? (And similarly for HashSet.) If this is the case, then perhaps difference and intersection could be defined in terms of this new primitive: difference a b = let (r, _, _) = symmetricDifference in r intersection a b = let (_, r, _) = symmetricDifference in r *if* it turns out that this does not degrade performance. Cheers Ben