-- Hoogle documentation, generated by Haddock
-- See Hoogle, http://www.haskell.org/hoogle/


-- | MaybeT monad transformer using transformers instead of mtl.
--   
--   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.
@package MaybeT-transformers
@version 0.1


-- | The <a>MaybeT</a> monad. See
--   <a>http://www.haskell.org/haskellwiki/New_monads/MaybeT</a> for more
--   widely-used version. Our <a>Functor</a> instance and our
--   implementation of <a>&gt;&gt;=</a> are borrowed from there.
--   
--   <ul>
--   <li><i>Computation type:</i> Computations which may fail or return
--   nothing.</li>
--   <li><i>Binding strategy:</i> Failure returns the value <a>Nothing</a>,
--   bypassing any bound functions which follow. Success returns a value
--   wrapped in <a>Just</a>.</li>
--   <li><i>Useful for:</i> Building computations from steps which may
--   fail. No error information is returned. (If error information is
--   required, see <tt>Control.Monad.Error</tt>.)</li>
--   </ul>
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)

-- | Lift a <a>Maybe</a> value to a <a>MaybeT</a>.
maybeT :: (Monad m) => Maybe a -> MaybeT m a

-- | Remove the <a>MaybeT</a> using a default value.
fromMaybeT :: (Monad m) => a -> MaybeT m a -> m a

-- | Remove the <a>MaybeT</a> using a monadic default value.
fromMaybeTM :: (Monad m) => m a -> MaybeT m a -> m 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) => MonadPlus (MaybeT m)
instance (Monad m) => Monad (MaybeT m)
instance (Functor m) => Functor (MaybeT m)