:: Map k v -> (v -> Bool) -> Map k v package:rio

filter :: (a -> Bool) -> Map k a -> Map k a
rio RIO.Map
O(n). Filter all values that satisfy the predicate. 
filter (> "a") (fromList [(5,"a"), (3,"b")]) == singleton 3 "b"
filter (> "x") (fromList [(5,"a"), (3,"b")]) == empty
filter (< "a") (fromList [(5,"a"), (3,"b")]) == empty