-- Hoogle documentation, generated by Haddock -- See Hoogle, http://www.haskell.org/hoogle/ -- | MaybeT monad transformer -- -- Support for computations with failures. @package MaybeT @version 0.1.1 -- | The MaybeT monad. See -- http://www.haskell.org/haskellwiki/New_monads/MaybeT for more -- widely-used version. Our Functor instance and our -- implementation of >>= are borrowed from there. -- -- module Control.Monad.Maybe -- | A monad transformer which adds Maybe semantics to an existing monad. newtype MaybeT m a MaybeT :: m (Maybe a) -> MaybeT m a runMaybeT :: MaybeT m a -> m (Maybe a) instance (MonadWriter w m) => MonadWriter w (MaybeT m) instance (MonadState s m) => MonadState s (MaybeT m) instance (MonadReader r m) => MonadReader r (MaybeT m) instance (MonadFix m) => MonadFix (MaybeT m) instance (MonadIO m) => MonadIO (MaybeT m) instance (MonadCont m) => MonadCont (MaybeT m) instance MonadTrans MaybeT instance (Monad m) => Monad (MaybeT m) instance (Functor m) => Functor (MaybeT m)