Copyright	(c) Dan Doel
License	BSD3
Maintainer	dan.doel@gmail.com
Stability	experimental
Portability	non-portable (multi-parameter type classes)
Safe Haskell	Safe
Language	Haskell2010

ListT

Description

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).

Synopsis

newtype ListT m a = ListT {
- unListT :: forall r. (a -> m r -> m r) -> m r -> m r
}
runListT :: ListT m a -> (a -> m r -> m r) -> m r -> m r
select :: Monad m => [a] -> ListT m a
fold :: ListT m a -> (a -> m r -> m r) -> m r -> m r

Documentation

newtype ListT m a Source #

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) #
Instance details Defined in ListT Methods (>>=) :: ListT m a -> (a -> ListT m b) -> ListT m b Source # (>>) :: ListT m a -> ListT m b -> ListT m b Source # return :: a -> ListT m a Source # fail :: String -> ListT m a Source #
Functor (ListT f) #
Instance details Defined in ListT Methods fmap :: (a -> b) -> ListT f a -> ListT f b Source # (<$) :: a -> ListT f b -> ListT f a Source #
MonadFail (ListT m) #
Instance details Defined in ListT Methods fail :: String -> ListT m a Source #
Applicative (ListT f) #
Instance details Defined in ListT Methods pure :: a -> ListT f a Source # (<>) :: ListT f (a -> b) -> ListT f a -> ListT f b Source # liftA2 :: (a -> b -> c) -> ListT f a -> ListT f b -> ListT f c Source # (>) :: ListT f a -> ListT f b -> ListT f b Source # (<*) :: ListT f a -> ListT f b -> ListT f a Source #
Alternative (ListT f) #
Instance details Defined in ListT Methods empty :: ListT f a Source # (<\|>) :: ListT f a -> ListT f a -> ListT f a Source # some :: ListT f a -> ListT f [a] Source # many :: ListT f a -> ListT f [a] Source #
MonadPlus (ListT m) #
Instance details Defined in ListT Methods mzero :: ListT m a Source # mplus :: ListT m a -> ListT m a -> ListT m a Source #

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

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

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