Control.Comonad.Hoist.Class

Documentation

class ComonadHoist t where

Methods

cohoist :: Comonad w => t w a -> t Identity a

Ideally we would offer a way to lift comonad homomorphisms but this isn't Haskell 98, so we settle for the most common case here.

 liftTrans :: (forall a. w a -> v a) -> t w a -> t v a 
 cohoist = liftTrans (Identity . extract)

Instances

ComonadHoist IdentityT

ComonadHoist (EnvT e)

ComonadHoist (StoreT s)

(Semigroup m, Monoid m) => ComonadHoist (TracedT m)