MaybeT -package

MaybeT :: m (Maybe a) -> MaybeT m a
transformers Control.Monad.Trans.Maybe
newtype MaybeT m a
transformers Control.Monad.Trans.Maybe
The parameterizable maybe monad, obtained by composing an arbitrary monad with the Maybe monad. Computations are actions that may produce a value or fail. The return function yields a successful computation, while >>= sequences two subcomputations, failing on the first error.
maybeToList :: Maybe a -> [a]
base Data.Maybe
The maybeToList function returns an empty list when given Nothing or a singleton list when not given Nothing.
mapMaybeT :: (m (Maybe a) -> n (Maybe b)) -> MaybeT m a -> MaybeT n b
transformers Control.Monad.Trans.Maybe
Transform the computation inside a MaybeT. *  (mapMaybeT f m) = f (runMaybeT >  
runMaybeT :: MaybeT m a -> m (Maybe a)
transformers Control.Monad.Trans.Maybe