foldMap package:containers

foldMap :: Monoid a => (Key -> a) -> IntSet -> a
containers Data.IntSet Data.IntSet.Internal
Map the elements in the set to a monoid and combine with (<>).
foldMapWithKey :: Monoid m => (Key -> a -> m) -> IntMap a -> m
containers Data.IntMap.Internal Data.IntMap.Lazy Data.IntMap.Strict Data.IntMap.Strict.Internal
Fold the keys and values in the map using the given monoid, such that 
foldMapWithKey f = fold . mapWithKey f
This can be an asymptotically faster than foldrWithKey or foldlWithKey for some monoids.
foldMapWithKey :: Monoid m => (k -> a -> m) -> Map k a -> m
containers Data.Map.Internal Data.Map.Lazy Data.Map.Strict Data.Map.Strict.Internal
Fold the keys and values in the map using the given monoid, such that 
foldMapWithKey f = fold . mapWithKey f
This can be an asymptotically faster than foldrWithKey or foldlWithKey for some monoids.
foldMapWithIndex :: Monoid m => (Int -> a -> m) -> Seq a -> m
containers Data.Sequence Data.Sequence.Internal