ListT

A backtracking, logic programming monad.

Adapted from the paper /Backtracking, Interleaving, and Terminating Monad Transformers/, by Oleg Kiselyov, Chung-chieh Shan, Daniel P. Friedman, Amr Sabry (http://www.cs.rutgers.edu/~ccshan/logicprog/ListT-icfp2005.pdf).

Documentation

newtype ListT m a

A monad transformer for performing backtracking computations layered over another monad m

Constructors

ListT

Fields

• unListT :: forall r. (a -> m r -> m r) -> m r -> m r

Instances

Monad (ListT m)

Defined in ListT

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 (ListT f)

Defined in ListT

Methods

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

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

MonadFail (ListT m)

Defined in ListT

Methods

fail :: String -> ListT m a

Applicative (ListT f)

Defined in ListT

Methods

pure :: a -> ListT f a

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

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

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

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

Alternative (ListT f)

Defined in ListT

Methods

empty :: ListT f a

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

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

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

MonadPlus (ListT m)

Defined in ListT

Methods

mzero :: ListT m a

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

runListT :: ListT m a -> (a -> m r -> m r) -> m r -> m r

Runs a ListT computation with the specified initial success and failure continuations.

select :: Monad m => [a] -> ListT m a

fold :: ListT m a -> (a -> m r -> m r) -> m r -> m r