module Data.Semigroup.Traversable
( Traversable1(..)
, foldMap1Default
) where
import Control.Applicative
import Control.Monad.Trans.Identity
import Data.Functor.Identity
import Data.Functor.Apply
import Data.Functor.Product
import Data.Functor.Compose
import Data.Semigroup.Foldable
import Data.Traversable
import Data.Semigroup hiding (Product)
import Data.Traversable.Instances ()
class (Foldable1 t, Traversable t) => Traversable1 t where
traverse1 :: Apply f => (a -> f b) -> t a -> f (t b)
sequence1 :: Apply f => t (f b) -> f (t b)
sequence1 = traverse1 id
traverse1 f = sequence1 . fmap f
foldMap1Default :: (Traversable1 f, Semigroup m) => (a -> m) -> f a -> m
foldMap1Default f = getConst . traverse1 (Const . f)
instance Traversable1 Identity where
traverse1 f = fmap Identity . f . runIdentity
instance Traversable1 f => Traversable1 (IdentityT f) where
traverse1 f = fmap IdentityT . traverse1 f . runIdentityT
instance (Traversable1 f, Traversable1 g) => Traversable1 (Compose f g) where
traverse1 f = fmap Compose . traverse1 (traverse1 f) . getCompose
instance (Traversable1 f, Traversable1 g) => Traversable1 (Product f g) where
traverse1 f (Pair a b) = Pair <$> traverse1 f a <.> traverse1 f b