Data.StarToStar.Contra

Instances for the fundamental * -> * types that require contravariance. Another O is defined to disambiguate the two valid Functor and Cofunctor instances.

Documentation

newtype O f g a

Constructors

O (f (g a))

Instances

(Cofunctor f, Cofunctor g) => Functor (O f g)

(Cofunctor f, Functor g) => Cofunctor (O f g)

onO :: (f (g a) -> b) -> O f g a -> b

underO :: (f (g a) -> h (i b)) -> O f g a -> O h i b

toO :: f (g a) -> O f g a

fromO :: O f g a -> f (g a)