module Data.Functor.Constant where

import Control.Functor.Covariant (Covariant ((<$>)))
import Control.Functor.Covariant.Pointable (Pointable (point))
import Control.Functor.Covariant.Composition.Traversable (Traversable ((->>)))
import Control.Functor.Contravariant (Contravariant ((>$<)))

newtype Constant a b = Constant a

instance Covariant (Constant a) where
	_ <$> Constant x = Constant x

instance Contravariant (Constant a) where
	_ >$< Constant x = Constant x

instance Traversable (Constant a) where
	Constant x ->> _ = point (Constant x)