Cale Gibbard and Ryan Trinkle are interested in adding some more operations they say will be useful in their work. Note that unionWithMapping is intended to enable an efficient implementation of alignWith in Data.Align in the `these` package. Set: filterIncreasing :: Ord a => (a -> Bool) -> Set a -> Set a filterDecreasing :: Ord a => (a -> Bool) -> Set a -> Set a partitionIncreasing :: Ord a => (a -> Bool) -> Set a -> (Set a, Set a) Map: filterKeysIncreasing :: Ord k => (k -> Bool) -> Map k a -> Map k a filterKeysDecreasing :: Ord k => (k -> Bool) -> Map k a -> Map k a partitionKeysIncreasing :: Ord k => (k -> Bool) -> Map k a -> (Map k a, Map k a) traverseMaybe :: Applicative f => (a -> f (Maybe b)) -> Map k a -> f (Map k b) alterMany :: Ord k => (a -> Maybe b -> Maybe b) -> Map k a -> Map k b -> Map k b alterManyA :: (Applicative f, Ord k) => (a -> Maybe b -> f (Maybe b)) -> Map k a -> Map k b -> f (Map k b) unionWithMapping :: Ord k => (a -> c) -> (b -> c) -> (a -> b -> c) -> Map k a -> Map k b -> Map k c unionWithKeyMapping :: Ord k => (k -> a -> c) -> (k -> b -> c) -> (k -> a -> b -> c) -> Map k a -> Map k b -> Map k c