Control.Monad.Trans.Contravariant.Adjoint

Uses a contravariant adjunction:

f -| g : Hask^op -> Hask

to build a Comonad to Monad transformer. Sadly, the dual construction, which builds a Comonad out of a Monad, is uninhabited, because any Adjunction of the form

f -| g : Hask -> Hask^op

would trivially admit unsafePerformIO.

Documentation

type Adjoint f g = AdjointT f g Identity

runAdjoint :: Contravariant g => Adjoint f g a -> g (f a)

adjoint :: Contravariant g => g (f a) -> Adjoint f g a

newtype AdjointT f g w a

Constructors

AdjointT

Fields

• runAdjointT :: g (w (f a))

Instances

(Adjunction f g, Comonad w) => Monad (AdjointT f g w)

Methods

(>>=) :: AdjointT f g w a -> (a -> AdjointT f g w b) -> AdjointT f g w b

(>>) :: AdjointT f g w a -> AdjointT f g w b -> AdjointT f g w b

return :: a -> AdjointT f g w a

fail :: String -> AdjointT f g w a

(Adjunction f g, Functor w) => Functor (AdjointT f g w)

Methods

fmap :: (a -> b) -> AdjointT f g w a -> AdjointT f g w b

(<$) :: a -> AdjointT f g w b -> AdjointT f g w a

(Adjunction f g, Comonad w) => Applicative (AdjointT f g w)

Methods

pure :: a -> AdjointT f g w a

(<*>) :: AdjointT f g w (a -> b) -> AdjointT f g w a -> AdjointT f g w b

liftA2 :: (a -> b -> c) -> AdjointT f g w a -> AdjointT f g w b -> AdjointT f g w c

(*>) :: AdjointT f g w a -> AdjointT f g w b -> AdjointT f g w b

(<*) :: AdjointT f g w a -> AdjointT f g w b -> AdjointT f g w a