Data.Mapping.Util
insertIfAbsent :: Ord k => k -> v -> Map k v -> (v, Maybe (Map k v)) Source #
inserts key with value only if absent, returns map if changed
nonDefault :: Eq a => a -> a -> Maybe a Source #
For use in maps where we don't want to store default values
equating :: Eq a => (b -> a) -> b -> b -> Bool Source #
Helper function (not exported)