Safe Haskell	None
Language	Haskell2010

Control.Effect.Empty

Contents

Empty effect
Re-exports

Description

An effect modelling nondeterminism without choice (success or failure).

This can be seen as similar to Fail, but without an error message. The NonDet effect is the composition of Empty and Choice.

Predefined carriers:

Control.Carrier.Empty.Maybe.
If Empty is the last effect in a stack, it can be interpreted directly to a Maybe.

Since: 1.0.0.0

Synopsis

data Empty (m :: * -> *) k = Empty
empty :: Has Empty sig m => m a
guard :: Has Empty sig m => Bool -> m ()
class (HFunctor sig, Monad m) => Algebra sig m | m -> sig
type Has eff sig m = (Members eff sig, Algebra sig m)
run :: Identity a -> a

Empty effect

data Empty (m :: * -> *) k Source #

Since: 1.0.0.0

Constructors

Empty

Instances

Effect Empty Source #
Instance details Defined in Control.Effect.Empty.Internal Methods thread :: (Functor ctx, Monad m) => ctx () -> (forall x. ctx (m x) -> n (ctx x)) -> Empty m a -> Empty n (ctx a) Source #
HFunctor Empty Source #
Instance details Defined in Control.Effect.Empty.Internal Methods hmap :: Functor m => (forall x. m x -> n x) -> Empty m a -> Empty n a Source #
Algebra Empty Maybe Source #
Instance details Defined in Control.Algebra Methods alg :: Empty Maybe a -> Maybe a Source #
Algebra NonDet [] Source #
Instance details Defined in Control.Algebra Methods alg :: NonDet [] a -> [a] Source #
Functor (Empty m) Source #
Instance details Defined in Control.Effect.Empty.Internal Methods fmap :: (a -> b) -> Empty m a -> Empty m b # (<$) :: a -> Empty m b -> Empty m a #
Generic1 (Empty m :: Type -> Type) Source #
Instance details Defined in Control.Effect.Empty.Internal Associated Types type Rep1 (Empty m) :: k -> Type # Methods from1 :: Empty m a -> Rep1 (Empty m) a # to1 :: Rep1 (Empty m) a -> Empty m a #
(Algebra sig m, Effect sig) => Algebra (Empty :+: sig) (EmptyC m) Source #
Instance details Defined in Control.Carrier.Empty.Maybe Methods alg :: (Empty :+: sig) (EmptyC m) a -> EmptyC m a Source #
(Algebra sig m, Effect sig) => Algebra (NonDet :+: sig) (NonDetC m) Source #
Instance details Defined in Control.Carrier.NonDet.Church Methods alg :: (NonDet :+: sig) (NonDetC m) a -> NonDetC m a Source #
(Algebra sig m, Effect sig) => Algebra (Cut :+: (NonDet :+: sig)) (CutC m) Source #
Instance details Defined in Control.Carrier.Cut.Church Methods alg :: (Cut :+: (NonDet :+: sig)) (CutC m) a -> CutC m a Source #
(Algebra sig m, Effect sig) => Algebra (Cull :+: (NonDet :+: sig)) (CullC m) Source #
Instance details Defined in Control.Carrier.Cull.Church Methods alg :: (Cull :+: (NonDet :+: sig)) (CullC m) a -> CullC m a Source #
type Rep1 (Empty m :: Type -> Type) Source #
Instance details Defined in Control.Effect.Empty.Internal type Rep1 (Empty m :: Type -> Type) = D1 (MetaData "Empty" "Control.Effect.Empty.Internal" "fused-effects-1.0.0.0-inplace" False) (C1 (MetaCons "Empty" PrefixI False) (U1 :: Type -> Type))

empty :: Has Empty sig m => m a Source #

Abort the computation.

empty annihilates >>=:

empty >>= k = empty

Since: 1.0.0.0

guard :: Has Empty sig m => Bool -> m () Source #

Conditional failure, returning only if the condition is True.

Since: 1.0.0.0

Re-exports

class (HFunctor sig, Monad m) => Algebra sig m | m -> sig Source #

The class of carriers (results) for algebras (effect handlers) over signatures (effects), whose actions are given by the alg method.

Since: 1.0.0.0

Minimal complete definition

alg

Instances

Algebra Choose NonEmpty Source #
Instance details Defined in Control.Algebra Methods alg :: Choose NonEmpty a -> NonEmpty a Source #
Algebra Empty Maybe Source #
Instance details Defined in Control.Algebra Methods alg :: Empty Maybe a -> Maybe a Source #
Algebra NonDet [] Source #
Instance details Defined in Control.Algebra Methods alg :: NonDet [] a -> [a] Source #
Algebra sig m => Algebra sig (IdentityT m) Source #
Instance details Defined in Control.Algebra Methods alg :: sig (IdentityT m) a -> IdentityT m a Source #
Algebra (Lift IO) IO Source #
Instance details Defined in Control.Algebra Methods alg :: Lift IO IO a -> IO a Source #
Algebra (Lift Identity) Identity Source #
Instance details Defined in Control.Algebra Methods alg :: Lift Identity Identity a -> Identity a Source #
Monad m => Algebra (Lift m) (LiftC m) Source #
Instance details Defined in Control.Carrier.Lift Methods alg :: Lift m (LiftC m) a -> LiftC m a Source #
Algebra (Error e) (Either e) Source #
Instance details Defined in Control.Algebra Methods alg :: Error e (Either e) a -> Either e a Source #
Monoid w => Algebra (Writer w) ((,) w) Source #
Instance details Defined in Control.Algebra Methods alg :: Writer w ((,) w) a -> (w, a) Source #
Algebra (Reader r) ((->) r :: Type -> Type) Source #
Instance details Defined in Control.Algebra Methods alg :: Reader r ((->) r) a -> r -> a Source #
(Algebra sig m, Effect sig) => Algebra (Choose :+: sig) (ChooseC m) Source #
Instance details Defined in Control.Carrier.Choose.Church Methods alg :: (Choose :+: sig) (ChooseC m) a -> ChooseC m a Source #
(Algebra sig m, Effect sig) => Algebra (Empty :+: sig) (EmptyC m) Source #
Instance details Defined in Control.Carrier.Empty.Maybe Methods alg :: (Empty :+: sig) (EmptyC m) a -> EmptyC m a Source #
(Algebra sig m, Effect sig) => Algebra (NonDet :+: sig) (NonDetC m) Source #
Instance details Defined in Control.Carrier.NonDet.Church Methods alg :: (NonDet :+: sig) (NonDetC m) a -> NonDetC m a Source #
(MonadIO m, Algebra sig m) => Algebra (Trace :+: sig) (TraceC m) Source #
Instance details Defined in Control.Carrier.Trace.Printing Methods alg :: (Trace :+: sig) (TraceC m) a -> TraceC m a Source #
Algebra sig m => Algebra (Trace :+: sig) (TraceC m) Source #
Instance details Defined in Control.Carrier.Trace.Ignoring Methods alg :: (Trace :+: sig) (TraceC m) a -> TraceC m a Source #
(Algebra sig m, Effect sig) => Algebra (Trace :+: sig) (TraceC m) Source #
Instance details Defined in Control.Carrier.Trace.Returning Methods alg :: (Trace :+: sig) (TraceC m) a -> TraceC m a Source #
(Algebra sig m, Effect sig) => Algebra (Fail :+: sig) (FailC m) Source #
Instance details Defined in Control.Carrier.Fail.Either Methods alg :: (Fail :+: sig) (FailC m) a -> FailC m a Source #
(Algebra sig m, Effect sig) => Algebra (Fresh :+: sig) (FreshC m) Source #
Instance details Defined in Control.Carrier.Fresh.Strict Methods alg :: (Fresh :+: sig) (FreshC m) a -> FreshC m a Source #
(Algebra sig m, Effect sig) => Algebra (Cut :+: (NonDet :+: sig)) (CutC m) Source #
Instance details Defined in Control.Carrier.Cut.Church Methods alg :: (Cut :+: (NonDet :+: sig)) (CutC m) a -> CutC m a Source #
(Algebra sig m, Effect sig) => Algebra (Cull :+: (NonDet :+: sig)) (CullC m) Source #
Instance details Defined in Control.Carrier.Cull.Church Methods alg :: (Cull :+: (NonDet :+: sig)) (CullC m) a -> CullC m a Source #
Algebra sig m => Algebra (Reader r :+: sig) (ReaderT r m) Source #
Instance details Defined in Control.Algebra Methods alg :: (Reader r :+: sig) (ReaderT r m) a -> ReaderT r m a Source #
Algebra sig m => Algebra (Reader r :+: sig) (ReaderC r m) Source #
Instance details Defined in Control.Carrier.Reader Methods alg :: (Reader r :+: sig) (ReaderC r m) a -> ReaderC r m a Source #
(Algebra sig m, Effect sig) => Algebra (State s :+: sig) (StateT s m) Source #
Instance details Defined in Control.Algebra Methods alg :: (State s :+: sig) (StateT s m) a -> StateT s m a Source #
(Algebra sig m, Effect sig) => Algebra (State s :+: sig) (StateT s m) Source #
Instance details Defined in Control.Algebra Methods alg :: (State s :+: sig) (StateT s m) a -> StateT s m a Source #
(Algebra sig m, Effect sig) => Algebra (State s :+: sig) (StateC s m) Source #
Instance details Defined in Control.Carrier.State.Strict Methods alg :: (State s :+: sig) (StateC s m) a -> StateC s m a Source #
(Algebra sig m, Effect sig) => Algebra (State s :+: sig) (StateC s m) Source #
Instance details Defined in Control.Carrier.State.Lazy Methods alg :: (State s :+: sig) (StateC s m) a -> StateC s m a Source #
(Algebra sig m, Effect sig) => Algebra (Throw e :+: sig) (ThrowC e m) Source #
Instance details Defined in Control.Carrier.Throw.Either Methods alg :: (Throw e :+: sig) (ThrowC e m) a -> ThrowC e m a Source #
(Algebra sig m, Effect sig) => Algebra (Error e :+: sig) (ExceptT e m) Source #
Instance details Defined in Control.Algebra Methods alg :: (Error e :+: sig) (ExceptT e m) a -> ExceptT e m a Source #
(Algebra sig m, Effect sig) => Algebra (Error e :+: sig) (ErrorC e m) Source #
Instance details Defined in Control.Carrier.Error.Either Methods alg :: (Error e :+: sig) (ErrorC e m) a -> ErrorC e m a Source #
(Algebra sig m, Effect sig, Monoid w) => Algebra (Writer w :+: sig) (WriterT w m) Source #
Instance details Defined in Control.Algebra Methods alg :: (Writer w :+: sig) (WriterT w m) a -> WriterT w m a Source #
(Algebra sig m, Effect sig, Monoid w) => Algebra (Writer w :+: sig) (WriterT w m) Source #
Instance details Defined in Control.Algebra Methods alg :: (Writer w :+: sig) (WriterT w m) a -> WriterT w m a Source #
(Monoid w, Algebra sig m, Effect sig) => Algebra (Writer w :+: sig) (WriterC w m) Source #
Instance details Defined in Control.Carrier.Writer.Strict Methods alg :: (Writer w :+: sig) (WriterC w m) a -> WriterC w m a Source #
(HFunctor eff, HFunctor sig, Reifies s (Handler eff m), Monad m, Algebra sig m) => Algebra (eff :+: sig) (InterpretC s eff m) Source #
Instance details Defined in Control.Carrier.Interpret Methods alg :: (eff :+: sig) (InterpretC s eff m) a -> InterpretC s eff m a Source #
(Algebra sig m, Effect sig, Monoid w) => Algebra (Reader r :+: (Writer w :+: (State s :+: sig))) (RWST r w s m) Source #
Instance details Defined in Control.Algebra Methods alg :: (Reader r :+: (Writer w :+: (State s :+: sig))) (RWST r w s m) a -> RWST r w s m a Source #
(Algebra sig m, Effect sig, Monoid w) => Algebra (Reader r :+: (Writer w :+: (State s :+: sig))) (RWST r w s m) Source #
Instance details Defined in Control.Algebra Methods alg :: (Reader r :+: (Writer w :+: (State s :+: sig))) (RWST r w s m) a -> RWST r w s m a Source #

type Has eff sig m = (Members eff sig, Algebra sig m) Source #

m is a carrier for sig containing eff.

Note that if eff is a sum, it will be decomposed into multiple Member constraints. While this technically allows one to combine multiple unrelated effects into a single Has constraint, doing so has two significant drawbacks:

Due to a problem with recursive type families, this can lead to significantly slower compiles.
It defeats ghc’s warnings for redundant constraints, and thus can lead to a proliferation of redundant constraints as code is changed.

run :: Identity a -> a Source #

Run an action exhausted of effects to produce its final result value.

Since: 1.0.0.0