MHask.Comonad

Compare to comonad.Control.Comonad (Comonad)

Documentation

class Copointed t => Comonad t where

Dual of MHask.Monad

Methods

duplicate :: Monad m => t (t m) <~ t m

extend :: (Monad m, Monad n) => (m <~ t n) -> t m <~ t n

fmapComonad :: (Monad m, Monad n, Monad (t n), Comonad t) => (m <~ n) -> t m <~ t n

If you define your Comonad in terms of extend and extract, then you get a free implementation of fmap which can be used for Functor.