Control.Monad.Logic

logict-0.5.0.2: A backtracking logic-programming monad.

Copyright | (c) Dan Doel
License | BSD3
Maintainer | dan.doel@gmail.com
Stability | experimental
Portability | non-portable (multi-parameter type classes)
Safe Haskell | Safe
Language | Haskell98

Control.Monad.Logic

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
- type Logic = LogicT Identity
- logic :: (forall r. (a -> r -> r) -> r -> r) -> Logic a
- runLogic :: Logic a -> (a -> r -> r) -> r -> r
- observe :: Logic a -> a
- observeMany :: Int -> Logic a -> [a]
- observeAll :: Logic a -> [a]
- newtype LogicT m a = LogicT {
  - unLogicT :: forall r. (a -> m r -> m r) -> m r -> m r
  }
- 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

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 |
Fields unLogicT :: forall r. (a -> m r -> m r) -> m r -> m r

Instances

MonadTrans LogicT |
MonadError e m => MonadError e (LogicT m) |
MonadReader r m => MonadReader r (LogicT m) |
MonadState s m => MonadState s (LogicT m) |
Monad (LogicT m) |
Functor (LogicT f) |
Applicative (LogicT f) |
(Monad m, Foldable m) => Foldable (LogicT m) |
Traversable (LogicT Identity) |
Alternative (LogicT f) |
MonadPlus (LogicT m) |
MonadIO m => MonadIO (LogicT m) |
Monad m => MonadLogic (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