Algebra.Monad.Error

The MonadError class

class Monad m => MonadError e m | m -> e where

Methods

throw :: e -> m a

catch :: (e -> m a) -> m a -> m a

Instances

MonadError SomeException IO

MonadError Void []

MonadError Void Maybe

MonadError e (Either e)

Monad m => MonadError Void (ListT m)

MonadError e m => MonadError e (StateT s m)

(Monoid w, MonadError e m) => MonadError e (RWST r w s m)

try :: MonadError e m => m a -> m a -> m a

(!+) :: MonadError Void m => m a -> m a -> m a

tryMay :: MonadError e m => m a -> m (Maybe a)

throwIO :: Exception e => e -> IO ()

The Either transformer

data EitherT e m a

Instances

MonadTrans (EitherT e)

Unit m => Unit (EitherT e m)

MonadFix m => MonadFix (EitherT e m)

Traversable m => Traversable (EitherT e m)

Foldable m => Foldable (EitherT e m)

Monad m => Monad (EitherT e m)

Applicative m => Applicative (EitherT e m)

Functor m => Functor (EitherT e m)

_eitherT :: Functor m => Iso (EitherT e m a) (EitherT f m b) (m (e :+: a)) (m (f :+: b))