Safe Haskell	None
Language	Haskell2010

Control.Effect.Cut

Synopsis

data Cut m k
- = Cutfail
- | Call (m a) (a -> k)
cutfail :: (Carrier sig m, Member Cut sig) => m a
call :: (Carrier sig m, Member Cut sig) => m a -> m a
cut :: (Alternative m, Carrier sig m, Member Cut sig) => m ()
runCut :: Alternative m => CutC m a -> m a
runCutAll :: (Alternative f, Applicative m) => CutC m a -> m (f a)
newtype CutC m a = CutC {
- runCutC :: forall b. (a -> m b -> m b) -> m b -> m b -> m b
}

Documentation

data Cut m k Source #

Cut effects are used with NonDet to provide control over backtracking.

Constructors

Cutfail
Call (m a) (a -> k)

Instances

Effect Cut Source #
Instance details Defined in Control.Effect.Cut Methods handle :: Functor f => f () -> (forall x. f (m x) -> n (f x)) -> Cut m (m a) -> Cut n (n (f a)) Source #
HFunctor Cut Source #
Instance details Defined in Control.Effect.Cut Methods fmap' :: (a -> b) -> Cut m a -> Cut m b Source # hmap :: (forall x. m x -> n x) -> Cut m a -> Cut n a Source #
Functor (Cut m) Source #
Instance details Defined in Control.Effect.Cut Methods fmap :: (a -> b) -> Cut m a -> Cut m b # (<$) :: a -> Cut m b -> Cut m a #
(Carrier sig m, Effect sig) => Carrier (Cut :+: (NonDet :+: sig)) (CutC m) Source #
Instance details Defined in Control.Effect.Cut Methods eff :: (Cut :+: (NonDet :+: sig)) (CutC m) (CutC m a) -> CutC m a Source #

cutfail :: (Carrier sig m, Member Cut sig) => m a Source #

Fail the current branch, and prevent backtracking within the nearest enclosing call (if any).

Contrast with empty, which fails the current branch but allows backtracking.

run (runNonDet (runCut (cutfail <|> pure a))) == []

run (runNonDet (runCut (pure a <|> cutfail))) == [a]

call :: (Carrier sig m, Member Cut sig) => m a -> m a Source #

Delimit the effect of cutfails, allowing backtracking to resume.

run (runNonDet (runCut (call (cutfail <|> pure a) <|> pure b))) == [b]

cut :: (Alternative m, Carrier sig m, Member Cut sig) => m () Source #

Commit to the current branch, preventing backtracking within the nearest enclosing call (if any) on failure.

run (runNonDet (runCut (pure a <|> cut *> pure b))) == [a, b]

run (runNonDet (runCut (cut *> pure a <|> pure b))) == [a]

run (runNonDet (runCut (cut *> empty <|> pure a))) == []

runCut :: Alternative m => CutC m a -> m a Source #

Run a Cut effect within an underlying Alternative instance (typically another Carrier for a NonDet effect).

run (runNonDetOnce (runCut (pure a))) == Just a

runCutAll :: (Alternative f, Applicative m) => CutC m a -> m (f a) Source #

Run a Cut effect, returning all its results in an Alternative collection.

newtype CutC m a Source #

Constructors

CutC
Fields runCutC :: forall b. (a -> m b -> m b) -> m b -> m b -> m b A higher-order function receiving three parameters: a function to combine each solution with the rest of the solutions, an action to run when no results are produced (e.g. on `empty`), and an action to run when no results are produced and backtrcking should not be attempted (e.g. on `cutfail`).

Instances

MonadTrans CutC Source #
Instance details Defined in Control.Effect.Cut Methods lift :: Monad m => m a -> CutC m a #
Monad (CutC m) Source #
Instance details Defined in Control.Effect.Cut Methods (>>=) :: CutC m a -> (a -> CutC m b) -> CutC m b # (>>) :: CutC m a -> CutC m b -> CutC m b # return :: a -> CutC m a # fail :: String -> CutC m a #
Functor (CutC m) Source #
Instance details Defined in Control.Effect.Cut Methods fmap :: (a -> b) -> CutC m a -> CutC m b # (<$) :: a -> CutC m b -> CutC m a #
MonadFail m => MonadFail (CutC m) Source #
Instance details Defined in Control.Effect.Cut Methods fail :: String -> CutC m a #
Applicative (CutC m) Source #
Instance details Defined in Control.Effect.Cut Methods pure :: a -> CutC m a # (<>) :: CutC m (a -> b) -> CutC m a -> CutC m b # liftA2 :: (a -> b -> c) -> CutC m a -> CutC m b -> CutC m c # (>) :: CutC m a -> CutC m b -> CutC m b # (<*) :: CutC m a -> CutC m b -> CutC m a #
MonadIO m => MonadIO (CutC m) Source #
Instance details Defined in Control.Effect.Cut Methods liftIO :: IO a -> CutC m a #
Alternative (CutC m) Source #
Instance details Defined in Control.Effect.Cut Methods empty :: CutC m a # (<\|>) :: CutC m a -> CutC m a -> CutC m a # some :: CutC m a -> CutC m [a] # many :: CutC m a -> CutC m [a] #
MonadPlus (CutC m) Source #
Instance details Defined in Control.Effect.Cut Methods mzero :: CutC m a # mplus :: CutC m a -> CutC m a -> CutC m a #
(Carrier sig m, Effect sig) => Carrier (Cut :+: (NonDet :+: sig)) (CutC m) Source #
Instance details Defined in Control.Effect.Cut Methods eff :: (Cut :+: (NonDet :+: sig)) (CutC m) (CutC m a) -> CutC m a Source #