-- | /O(log n)/. Performs a 'split' but also returns whether the pivot
-- element was found in the original set.
splitMember :: Ord a => a -> Set a -> (Set a,Bool,Set a)
splitMember _ Tip = (Tip, False, Tip)
splitMember :: Ord a => a -> Set a -> (Set a,Bool,Set a)
splitMember _ Tip = (Tip, False, Tip)
splitMember _ Tip = (Tip, False, Tip)