pandora-0.4.4: Pandora/Pattern/Functor/Distributive.hs

module Pandora.Pattern.Functor.Distributive where

import Pandora.Pattern.Functor.Covariant (Covariant_)

{- |
> Let f :: Distributive g => (a -> g b)

> When providing a new instance, you should ensure it satisfies:
> * Identity morphism: (identity -<<) . (identity -<<) ≡ identity
> * Interchange collection: (f -<<) ≡ (identity -<<) . (f -<$>-)
-}

infixl 5 -<<

class Covariant_ t source target => Distributive t source target where
	(-<<) :: Covariant_ u source target => source a (t b) -> target (u a) (t (u b))