current definition of foldMapA:
foldMapA :: forall b m f a . (Monoid b, Applicative m, Foldable f) => (a -> m b) -> f a -> m b
foldMapA f = foldr (\a mb -> liftA2 mappend (f a) mb) (pure mempty)
instead of using an explicit right fold, it might be better to use whatever foldMap is, using Data.Monoid.Ap:
newtype Ap f a = Ap { getAp :: f a }
deriving (Functor, Applicative)
instance (Applicative f, Semigroup a) => Semigroup (Ap f a) where
x <> y = liftA2 (<>) x y
instance (Applicative f, Monoid a) => Monoid (Ap f a) where
mempty = pure mempty
foldMapA :: (Monoid b, Foldable t, Applicative f) => (a -> f b) -> t a -> f b
foldMapA f = getAp . foldMap (Ap . f)definitions of foldMap are usually defined to be advantageous over the structure of a particular Foldable; using foldr is picking the direction of association, which seems unnecessary.
current definition of foldMapA:
instead of using an explicit right fold, it might be better to use whatever
foldMapis, usingData.Monoid.Ap:definitions of
foldMapare usually defined to be advantageous over the structure of a particular Foldable; using foldr is picking the direction of association, which seems unnecessary.