adjunctions-0.5.1: Data/Functor/Composition.hs

module Data.Functor.Composition 
  ( Composition(..) ) where

import Data.Functor.Compose
  
-- | We often need to distinguish between various forms of Functor-like composition in Haskell in order to please the type system.
-- This lets us work with these representations uniformly.
class Composition compose where
  decompose :: compose f g x -> f (g x)
  compose :: f (g x) -> compose f g x

instance Composition Compose where
  decompose = getCompose
  compose = Compose