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://okmij.org/ftp/papers/LogicT.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 Source #

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

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

A smart constructor for Logic computations.

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

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

observe :: Logic a -> a Source #

Extracts the first result from a Logic computation.

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

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

observeAll :: Logic a -> [a] Source #

Extracts all results from a Logic computation.

The LogicT monad transformer

newtype LogicT m a Source #

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 Source #
Instance details Defined in Control.Monad.Logic Methods lift :: Monad m => m a -> LogicT m a #
MonadState s m => MonadState s (LogicT m) Source #
Instance details Defined in Control.Monad.Logic Methods get :: LogicT m s # put :: s -> LogicT m () # state :: (s -> (a, s)) -> LogicT m a #
MonadReader r m => MonadReader r (LogicT m) Source #
Instance details Defined in Control.Monad.Logic Methods ask :: LogicT m r # local :: (r -> r) -> LogicT m a -> LogicT m a # reader :: (r -> a) -> LogicT m a #
MonadError e m => MonadError e (LogicT m) Source #
Instance details Defined in Control.Monad.Logic Methods throwError :: e -> LogicT m a # catchError :: LogicT m a -> (e -> LogicT m a) -> LogicT m a #
Monad (LogicT m) Source #
Instance details Defined in Control.Monad.Logic 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) Source #
Instance details Defined in Control.Monad.Logic Methods fmap :: (a -> b) -> LogicT f a -> LogicT f b # (<$) :: a -> LogicT f b -> LogicT f a #
MonadFail (LogicT m) Source #
Instance details Defined in Control.Monad.Logic Methods fail :: String -> LogicT m a #
Applicative (LogicT f) Source #
Instance details Defined in Control.Monad.Logic Methods pure :: a -> LogicT f a # (<>) :: LogicT f (a -> b) -> LogicT f a -> LogicT f b # liftA2 :: (a -> b -> c) -> LogicT f a -> LogicT f b -> LogicT f c # (>) :: 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) Source #
Instance details Defined in Control.Monad.Logic Methods fold :: Monoid m0 => LogicT m m0 -> m0 # foldMap :: Monoid m0 => (a -> m0) -> LogicT m a -> m0 # 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 #
Foldable (LogicT Identity) Source #
Instance details Defined in Control.Monad.Logic Methods fold :: Monoid m => LogicT Identity m -> m # foldMap :: Monoid m => (a -> m) -> LogicT Identity a -> m # foldr :: (a -> b -> b) -> b -> LogicT Identity a -> b # foldr' :: (a -> b -> b) -> b -> LogicT Identity a -> b # foldl :: (b -> a -> b) -> b -> LogicT Identity a -> b # foldl' :: (b -> a -> b) -> b -> LogicT Identity a -> b # foldr1 :: (a -> a -> a) -> LogicT Identity a -> a # foldl1 :: (a -> a -> a) -> LogicT Identity a -> a # toList :: LogicT Identity a -> [a] # null :: LogicT Identity a -> Bool # length :: LogicT Identity a -> Int # elem :: Eq a => a -> LogicT Identity a -> Bool # maximum :: Ord a => LogicT Identity a -> a # minimum :: Ord a => LogicT Identity a -> a # sum :: Num a => LogicT Identity a -> a # product :: Num a => LogicT Identity a -> a #
Traversable (LogicT Identity) Source #
Instance details Defined in Control.Monad.Logic 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) Source #
Instance details Defined in Control.Monad.Logic Methods liftIO :: IO a -> LogicT m a #
Alternative (LogicT f) Source #
Instance details Defined in Control.Monad.Logic 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) Source #
Instance details Defined in Control.Monad.Logic Methods mzero :: LogicT m a # mplus :: LogicT m a -> LogicT m a -> LogicT m a #
Monad m => MonadLogic (LogicT m) Source #
Instance details Defined in Control.Monad.Logic Methods msplit :: LogicT m a -> LogicT m (Maybe (a, LogicT m a)) Source # interleave :: LogicT m a -> LogicT m a -> LogicT m a Source # (>>-) :: LogicT m a -> (a -> LogicT m b) -> LogicT m b Source # ifte :: LogicT m a -> (a -> LogicT m b) -> LogicT m b -> LogicT m b Source # once :: LogicT m a -> LogicT m a Source # lnot :: LogicT m a -> LogicT m () Source #

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

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

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

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

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

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

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

Extracts all results from a LogicT computation.

module Control.Monad

module Control.Monad.Trans