logict-0.6.0.2: 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 # |
Methods lift :: Monad m => m a -> LogicT m a #
MonadError e m => MonadError e (LogicT m) # |
Methods throwError :: e -> LogicT m a # catchError :: LogicT m a -> (e -> LogicT m a) -> LogicT m a #
MonadReader r m => MonadReader r (LogicT m) # |
Methods ask :: LogicT m r # local :: (r -> r) -> LogicT m a -> LogicT m a # reader :: (r -> a) -> LogicT m a #
MonadState s m => MonadState s (LogicT m) # |
Methods get :: LogicT m s # put :: s -> LogicT m () # state :: (s -> (a, s)) -> LogicT m a #
Monad (LogicT m) # |
Methods (>>=) :: LogicT m a -> (a -> LogicT m b) -> LogicT m b # (>>) :: LogicT m a -> LogicT m b -> LogicT m b # return :: a -> LogicT m a # fail :: String -> LogicT m a #
Functor (LogicT f) # |
Methods fmap :: (a -> b) -> LogicT f a -> LogicT f b # (<$) :: a -> LogicT f b -> LogicT f a #
Applicative (LogicT f) # |
Methods pure :: a -> LogicT f a # (<*>) :: LogicT f (a -> b) -> LogicT f a -> LogicT f b # (*>) :: LogicT f a -> LogicT f b -> LogicT f b # (<*) :: LogicT f a -> LogicT f b -> LogicT f a #
(Monad m, Foldable m) => Foldable (LogicT m) # |
Methods fold :: Monoid m => LogicT m m -> m # foldMap :: Monoid m => (a -> m) -> LogicT m a -> m # foldr :: (a -> b -> b) -> b -> LogicT m a -> b # foldr' :: (a -> b -> b) -> b -> LogicT m a -> b # foldl :: (b -> a -> b) -> b -> LogicT m a -> b # foldl' :: (b -> a -> b) -> b -> LogicT m a -> b # foldr1 :: (a -> a -> a) -> LogicT m a -> a # foldl1 :: (a -> a -> a) -> LogicT m a -> a # toList :: LogicT m a -> [a] # null :: LogicT m a -> Bool # length :: LogicT m a -> Int # elem :: Eq a => a -> LogicT m a -> Bool # maximum :: Ord a => LogicT m a -> a # minimum :: Ord a => LogicT m a -> a # sum :: Num a => LogicT m a -> a # product :: Num a => LogicT m a -> a #
Traversable (LogicT Identity) # |
Methods traverse :: Applicative f => (a -> f b) -> LogicT Identity a -> f (LogicT Identity b) # sequenceA :: Applicative f => LogicT Identity (f a) -> f (LogicT Identity a) # mapM :: Monad m => (a -> m b) -> LogicT Identity a -> m (LogicT Identity b) # sequence :: Monad m => LogicT Identity (m a) -> m (LogicT Identity a) #
MonadIO m => MonadIO (LogicT m) # |
Methods liftIO :: IO a -> LogicT m a #
Alternative (LogicT f) # |
Methods empty :: LogicT f a # (<|>) :: LogicT f a -> LogicT f a -> LogicT f a # some :: LogicT f a -> LogicT f [a] # many :: LogicT f a -> LogicT f [a] #
MonadPlus (LogicT m) # |
Methods mzero :: LogicT m a # mplus :: LogicT m a -> LogicT m a -> LogicT m a #
Monad m => MonadLogic (LogicT m) # |
Methods msplit :: LogicT m a -> LogicT m (Maybe (a, LogicT m a)) # interleave :: LogicT m a -> LogicT m a -> LogicT m a # (>>-) :: LogicT m a -> (a -> LogicT m b) -> LogicT m b # ifte :: LogicT m a -> (a -> LogicT m b) -> LogicT m b -> LogicT m b # once :: LogicT m a -> LogicT m a #

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