logict-0.6.0.2: A backtracking logic-programming monad.

Copyright (c) Dan Doel BSD3 dan.doel@gmail.com experimental non-portable (multi-parameter type classes) Safe Haskell98

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/LogicT-icfp2005.pdf).

Synopsis

Documentation

type Logic = LogicT Identity #

The basic Logic monad, for performing backtracking computations returning values of type a

logic :: (forall r. (a -> r -> r) -> r -> r) -> Logic a #

A smart constructor for Logic computations.

runLogic :: Logic a -> (a -> r -> r) -> r -> r #

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

observe :: Logic a -> a #

Extracts the first result from a Logic computation.

observeMany :: Int -> Logic a -> [a] #

Extracts up to a given number of results from a Logic computation.

observeAll :: Logic a -> [a] #

Extracts all results from a Logic computation.

The LogicT monad transformer

newtype LogicT m a #

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

Constructors

 LogicT FieldsunLogicT :: forall r. (a -> m r -> m r) -> m r -> m r

Instances

runLogicT :: LogicT m a -> (a -> m r -> m r) -> m r -> m r #

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

observeT :: Monad m => LogicT m a -> m a #

Extracts the first result from a LogicT computation, failing otherwise.

observeManyT :: Monad m => Int -> LogicT m a -> m [a] #

Extracts up to a given number of results from a LogicT computation.

observeAllT :: Monad m => LogicT m a -> m [a] #

Extracts all results from a LogicT computation.