+-- | /O(n)/. Map values and collect the 'Just' results.
+mapMaybe :: Ord k => (a -> Maybe b) -> Map k a -> Map k b
+mapMaybe f m
+ = mapMaybeWithKey (\k x -> f x) m
+
+-- | /O(n)/. Map keys\/values and collect the 'Just' results.
+mapMaybeWithKey :: Ord k => (k -> a -> Maybe b) -> Map k a -> Map k b
+mapMaybeWithKey f Tip = Tip
+mapMaybeWithKey f (Bin _ kx x l r) = case f kx x of
+ Just y -> join kx y (mapMaybeWithKey f l) (mapMaybeWithKey f r)
+ Nothing -> merge (mapMaybeWithKey f l) (mapMaybeWithKey f r)
+
+-- | /O(n)/. Map values and separate the 'Left' and 'Right' results.
+mapEither :: Ord k => (a -> Either b c) -> Map k a -> (Map k b, Map k c)
+mapEither f m
+ = mapEitherWithKey (\k x -> f x) m
+
+-- | /O(n)/. Map keys\/values and separate the 'Left' and 'Right' results.
+mapEitherWithKey :: Ord k =>
+ (k -> a -> Either b c) -> Map k a -> (Map k b, Map k c)
+mapEitherWithKey f Tip = (Tip, Tip)
+mapEitherWithKey f (Bin _ kx x l r) = case f kx x of
+ Left y -> (join kx y l1 r1, merge l2 r2)
+ Right z -> (merge l1 r1, join kx z l2 r2)
+ where
+ (l1,l2) = mapEitherWithKey f l
+ (r1,r2) = mapEitherWithKey f r