Control.Monad.Logic

Portability	non-portable (multi-parameter type classes)
Stability	experimental
Maintainer	dan.doel@gmail.com

Contents

The Logic monad
The LogicT monad transformer

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

module Control.Monad.Logic.Class

data Logic a

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

observe :: Logic a -> a

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

observeAll :: Logic a -> [a]

data LogicT m a

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

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

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

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

module Control.Monad

module Control.Monad.Trans

Documentation

module Control.Monad.Logic.Class

The Logic monad

data Logic a

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

Instances

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

data LogicT m a

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

Instances

MonadTrans LogicT

MonadReader r m => MonadReader r (LogicT m)

MonadState s m => MonadState s (LogicT m)

Applicative f => Alternative (LogicT f)

Applicative f => Applicative (LogicT f)

Functor f => Functor (LogicT f)

Monad m => Monad (LogicT m)

MonadIO m => MonadIO (LogicT m)

Monad m => MonadLogic (LogicT m)

Monad m => MonadPlus (LogicT m)

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.

module Control.Monad

module Control.Monad.Trans

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