Control.Monad.Trans.List

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

The ListT monad transformer

newtype ListT m a

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

Methods

lift :: Monad m => m a -> ListT m a

Monad m => Monad (ListT m)

Methods

(>>=) :: ListT m a -> (a -> ListT m b) -> ListT m b

(>>) :: ListT m a -> ListT m b -> ListT m b

return :: a -> ListT m a

fail :: String -> ListT m a

Functor m => Functor (ListT m)

Methods

fmap :: (a -> b) -> ListT m a -> ListT m b

(<$) :: a -> ListT m b -> ListT m a

Monad m => MonadFail (ListT m)

Methods

fail :: String -> ListT m a

Applicative m => Applicative (ListT m)

Methods

pure :: a -> ListT m a

(<*>) :: ListT m (a -> b) -> ListT m a -> ListT m b

liftA2 :: (a -> b -> c) -> ListT m a -> ListT m b -> ListT m c

(*>) :: ListT m a -> ListT m b -> ListT m b

(<*) :: ListT m a -> ListT m b -> ListT m a

Foldable f => Foldable (ListT f)

Methods

fold :: Monoid m => ListT f m -> m

foldMap :: Monoid m => (a -> m) -> ListT f a -> m

foldr :: (a -> b -> b) -> b -> ListT f a -> b

foldr' :: (a -> b -> b) -> b -> ListT f a -> b

foldl :: (b -> a -> b) -> b -> ListT f a -> b

foldl' :: (b -> a -> b) -> b -> ListT f a -> b

foldr1 :: (a -> a -> a) -> ListT f a -> a

foldl1 :: (a -> a -> a) -> ListT f a -> a

toList :: ListT f a -> [a]

null :: ListT f a -> Bool

length :: ListT f a -> Int

elem :: Eq a => a -> ListT f a -> Bool

maximum :: Ord a => ListT f a -> a

minimum :: Ord a => ListT f a -> a

sum :: Num a => ListT f a -> a

product :: Num a => ListT f a -> a

Traversable f => Traversable (ListT f)

Methods

traverse :: Applicative f => (a -> f b) -> ListT f a -> f (ListT f b)

sequenceA :: Applicative f => ListT f (f a) -> f (ListT f a)

mapM :: Monad m => (a -> m b) -> ListT f a -> m (ListT f b)

sequence :: Monad m => ListT f (m a) -> m (ListT f a)

Eq1 m => Eq1 (ListT m)

Methods

liftEq :: (a -> b -> Bool) -> ListT m a -> ListT m b -> Bool

Ord1 m => Ord1 (ListT m)

Methods

liftCompare :: (a -> b -> Ordering) -> ListT m a -> ListT m b -> Ordering

Read1 m => Read1 (ListT m)

Methods

liftReadsPrec :: (Int -> ReadS a) -> ReadS [a] -> Int -> ReadS (ListT m a)

liftReadList :: (Int -> ReadS a) -> ReadS [a] -> ReadS [ListT m a]

liftReadPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec (ListT m a)

liftReadListPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec [ListT m a]

Show1 m => Show1 (ListT m)

Methods

liftShowsPrec :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> Int -> ListT m a -> ShowS

liftShowList :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> [ListT m a] -> ShowS

MonadZip m => MonadZip (ListT m)

Methods

mzip :: ListT m a -> ListT m b -> ListT m (a, b)

mzipWith :: (a -> b -> c) -> ListT m a -> ListT m b -> ListT m c

munzip :: ListT m (a, b) -> (ListT m a, ListT m b)

MonadIO m => MonadIO (ListT m)

Methods

liftIO :: IO a -> ListT m a

Applicative m => Alternative (ListT m)

Methods

empty :: ListT m a

(<|>) :: ListT m a -> ListT m a -> ListT m a

some :: ListT m a -> ListT m [a]

many :: ListT m a -> ListT m [a]

Monad m => MonadPlus (ListT m)

Methods

mzero :: ListT m a

mplus :: ListT m a -> ListT m a -> ListT m a

(Eq1 m, Eq a) => Eq (ListT m a)

Methods

(==) :: ListT m a -> ListT m a -> Bool

(/=) :: ListT m a -> ListT m a -> Bool

(Ord1 m, Ord a) => Ord (ListT m a)

Methods

compare :: ListT m a -> ListT m a -> Ordering

(<) :: ListT m a -> ListT m a -> Bool

(<=) :: ListT m a -> ListT m a -> Bool

(>) :: ListT m a -> ListT m a -> Bool

(>=) :: ListT m a -> ListT m a -> Bool

max :: ListT m a -> ListT m a -> ListT m a

min :: ListT m a -> ListT m a -> ListT m a

(Read1 m, Read a) => Read (ListT m a)

Methods

readsPrec :: Int -> ReadS (ListT m a)

readList :: ReadS [ListT m a]

readPrec :: ReadPrec (ListT m a)

readListPrec :: ReadPrec [ListT m a]

(Show1 m, Show a) => Show (ListT m a)

Methods

showsPrec :: Int -> ListT m a -> ShowS

show :: ListT m a -> String

showList :: [ListT m a] -> ShowS

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

Map between ListT computations.

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

Lifting other operations

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

Lift a callCC operation to the new monad.

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

Lift a catchE operation to the new monad.