Control.Monad.Maybe

This module introduces the MaybeT monad transformer. It is basically a simplification of the ErrorT monad transformer.

Documentation

newtype MaybeT m a

The monad transformer MaybeT.

Constructors

MaybeT

Fields

runMaybeT :: m (Maybe a)

Instances

MonadTrans MaybeT

MonadUnTrans MaybeAlg MaybeT

Unlifting the partiality monad transformer.

MonadReader r m => MonadReader r (MaybeT m)

MonadState s m => MonadState s (MaybeT m)

MonadWriter w m => MonadWriter w (MaybeT m)

Monad m => Monad (MaybeT m)

Monad m => Functor (MaybeT m)

MonadFix m => MonadFix (MaybeT m)

Monad m => MonadPlus (MaybeT m)

MonadIO m => MonadIO (MaybeT m)

MonadCont m => MonadCont (MaybeT m)