Control.Effect.Cut

Documentation

data Cut m k

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

Constructors

Cutfail

Call (m a) (a -> k)

Instances

Effect Cut

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))

HFunctor Cut

Defined in Control.Effect.Cut

Methods

fmap' :: (a -> b) -> Cut m a -> Cut m b

hmap :: (forall x. m x -> n x) -> Cut m a -> Cut n a

Functor (Cut m)

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)

Defined in Control.Effect.Cut

Methods

eff :: (Cut :+: (NonDet :+: sig)) (CutC m) (CutC m a) -> CutC m a

ret :: a -> CutC m a

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

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

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 ()

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

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)

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

newtype CutC m a

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

Defined in Control.Effect.Cut

Methods

lift :: Monad m => m a -> CutC m a

Monad (CutC m)

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)

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)

Defined in Control.Effect.Cut

Methods

fail :: String -> CutC m a

Applicative (CutC m)

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)

Defined in Control.Effect.Cut

Methods

liftIO :: IO a -> CutC m a

Alternative (CutC m)

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)

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)

Defined in Control.Effect.Cut

Methods

eff :: (Cut :+: (NonDet :+: sig)) (CutC m) (CutC m a) -> CutC m a

ret :: a -> CutC m a