MaybeT

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.
package MaybeT
package
Support for computations with failures. Version 0.1.2
package MaybeT-monads-tf
package
Support for computations with failures. This is a fork of the MaybeT package by Eric Kidd, but compatible with the type-family based monad classes of the monads-tf package. This package is deprecated: the MaybeT transformer exists in the transformers package nowadays, and the only advantage this package provides over that one is the presence of a MonadFix instance, but it's incorrect anyway. Version 0.2.0.1
package MaybeT-transformers
package
Support for computations with failures. This package is a fork from the MaybeT package by Eric Kidd, changed to depend on transformers instead of mtl. It also adds a few more utility functions. Version 0.2
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