Currently there is splitLookup :: Ord k => k -> Map k a -> (Maybe a,Map k a,Map k a) returning the matching element (if any) and the submaps less and greater than the key. I think it would be neater to return the element in the middle: splitLookup :: Ord k => k -> Map k a -> (Map k a,Maybe a,Map k a) Perhaps Data.Set.splitMember should similarly be changed from splitMember :: Ord a => a -> Set a -> (Bool,Set a,Set a) to splitMember :: Ord a => a -> Set a -> (Set a,Bool,Set a)