[Haskell-cafe] (Co/Contra)Functor and Comonad

Maciej Piechotka uzytkownik2 at gmail.com
Fri Dec 24 13:43:30 CET 2010

On Fri, 2010-12-24 at 05:36 -0500, Edward Kmett wrote:
> +1 for adding Comonads. As an aside, since Haskell doesn't have (nor
> could it have) coexponential objects, there is no 'missing'
> Coapplicative concept that goes with it, so there can be no objection
> on the grounds of lack of symmetry even if the Functor => Applicative
> => Monad proposal goes through.  

There is still potentially useful Copointed/CoPointed:

class [Functor a =>] CoPointed a where
    copoint :: f a -> a


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