Copyright	(c) Andy Gill 2001, (c) Oregon Graduate Institute of Science and Technology, 2001
License	BSD-style (see the file LICENSE)
Maintainer	ross@soi.city.ac.uk
Stability	experimental
Portability	portable
Safe Haskell	Safe-Inferred
Language	Haskell98

Control.Monad.Trans.List

Contents

Description

The ListT monad transformer, adding backtracking to a given monad, which must be commutative.

Synopsis

The ListT monad transformer

newtype ListT m a Source

Parameterizable list monad, with an inner monad.

Note: this does not yield a monad unless the argument monad is commutative.

Constructors

ListT
Fields runListT :: m [a]

Instances

MonadTrans ListT
Applicative m => Alternative (ListT m)
Monad m => Monad (ListT m)
Functor m => Functor (ListT m)
Monad m => MonadPlus (ListT m)
Applicative m => Applicative (ListT m)
Foldable f => Foldable (ListT f)
Traversable f => Traversable (ListT f)
MonadIO m => MonadIO (ListT m)

mapListT :: (m [a] -> n [b]) -> ListT m a -> ListT n b Source

Map between ListT computations.

runListT (mapListT f m) = f (runListT m)

Lifting other operations

liftCallCC :: ((([a] -> m [b]) -> m [a]) -> m [a]) -> ((a -> ListT m b) -> ListT m a) -> ListT m a Source

Lift a callCC operation to the new monad.

liftCatch :: (m [a] -> (e -> m [a]) -> m [a]) -> ListT m a -> (e -> ListT m a) -> ListT m a Source

Lift a catchError operation to the new monad.