Control.Monad.Either

Incompatible with Control.Monad.Error, but removes the Error restriction that prevents a natural encoding of Apomorphisms. This module is therefore incompatible with Control.Monad.Error

Documentation

data Either a b

The Either type represents values with two possibilities: a value of type Either a b is either Left a or Right b.

The Either type is sometimes used to represent a value which is either correct or an error; by convention, the Left constructor is used to hold an error value and the Right constructor is used to hold a correct value (mnemonic: "right" also means "correct").

Constructors

Left a

Right b

Instances

Typeable2 Either

Bifunctor Either

Coassociative Either

Associative Either

Symmetric Either

Braided Either

BiZap Either (,)

BiZap (,) Either

Monad (Either e)

Functor (Either a)

MonadFix (Either e)

Applicative (Either e)

Pointed (Either a)

Cozip (Either c)

Monoid a => Zip (Either a)

(Eq a, Eq b) => Eq (Either a b)

(Ord a, Ord b) => Ord (Either a b)

(Read a, Read b) => Read (Either a b)

(Show a, Show b) => Show (Either a b)

Representable (EitherF a b) (Either a b)

(Copointed f, Copointed g) => Copointed (BifunctorF Either f g)

Functor f => PPointed (BiffB Either Identity f)

Functor f => PApplicative (BiffB Either Identity f)

Functor f => PMonad (BiffB Either Identity f)

newtype EitherT a m b

Constructors

EitherT

Fields

runEitherT :: m (Either a b)

Instances

Monad m => Monad (EitherT a m)

Functor f => Functor (EitherT a f)

MonadFix m => MonadFix (EitherT a m)

Pointed f => Pointed (EitherT a f)