module Data.NonEmpty.Foldable where import qualified Data.Foldable as Fold import Data.Foldable (Foldable, ) {- | It holds: > foldMap f . Mapped g = foldMap f . fmap g but use of 'Mapped' avoids 'Functor' constraint. -} data Mapped f a b = Mapped (a -> b) (f a) instance (Foldable f) => Foldable (Mapped f a) where foldMap g (Mapped f xs) = Fold.foldMap (g . f) xs foldr g x (Mapped f xs) = Fold.foldr (g . f) x xs foldl g x (Mapped f xs) = Fold.foldl (\acc -> g acc . f) x xs