foldrWithKey package:rio

foldrWithKey :: (k -> v -> a -> a) -> a -> HashMap k v -> a
rio RIO.HashMap
Reduce this map by applying a binary operator to all elements, using the given starting value (typically the right-identity of the operator).
foldrWithKey :: (k -> a -> b -> b) -> b -> Map k a -> b
rio RIO.Map
Fold the keys and values in the map using the given right-associative binary operator, such that foldrWithKey f z == foldr (uncurry f) z . toAscList. For example, 
keys map = foldrWithKey (\k x ks -> k:ks) [] map

let f k a result = result ++ "(" ++ (show k) ++ ":" ++ a ++ ")"
foldrWithKey f "Map: " (fromList [(5,"a"), (3,"b")]) == "Map: (5:a)(3:b)"
foldrWithKey' :: (k -> a -> b -> b) -> b -> Map k a -> b
rio RIO.Map
A strict version of foldrWithKey. Each application of the operator is evaluated before using the result in the next application. This function is strict in the starting value.