Control.Effect.Lift

Provides a mechanism to kick off the evaluation of an effect stack that takes place in a monadic context.

Lift effects are always the last effect in a given effect stack. These stacks are invoked with runM or run.

Predefined carriers:

• Control.Carrier.Lift
• IO
• Identity

Since: 0.1.0.0

Lift effect

data Lift sig m k

Since: 1.0.0.0

Constructors

forall a. LiftWith (forall ctx. Functor ctx => ctx () -> (forall a. ctx (m a) -> sig (ctx a)) -> sig (ctx a)) (a -> m k)

Instances

Functor sig => Effect (Lift sig)

Defined in Control.Effect.Lift.Internal

Methods

thread :: (Functor ctx, Monad m) => ctx () -> (forall x. ctx (m x) -> n (ctx x)) -> Lift sig m a -> Lift sig n (ctx a)

HFunctor (Lift sig)

Defined in Control.Effect.Lift.Internal

Methods

hmap :: Functor m => (forall x. m x -> n x) -> Lift sig m a -> Lift sig n a

Algebra (Lift IO) IO

Defined in Control.Algebra

Methods

alg :: Lift IO IO a -> IO a

Algebra (Lift Identity) Identity

Defined in Control.Algebra

Methods

alg :: Lift Identity Identity a -> Identity a

Monad m => Algebra (Lift m) (LiftC m)

Defined in Control.Carrier.Lift

Methods

alg :: Lift m (LiftC m) a -> LiftC m a

Functor m => Functor (Lift sig m)

Defined in Control.Effect.Lift.Internal

Methods

fmap :: (a -> b) -> Lift sig m a -> Lift sig m b

(<$) :: a -> Lift sig m b -> Lift sig m a

sendM :: (Has (Lift n) sig m, Functor n) => n a -> m a

Given a Lift n constraint in a signature carried by m, sendM promotes arbitrary actions of type n a to m a. It is spiritually similar to lift from the MonadTrans typeclass.

Since: 1.0.0.0

liftWith :: Has (Lift n) sig m => (forall ctx. Functor ctx => ctx () -> (forall a. ctx (m a) -> n (ctx a)) -> n (ctx a)) -> m a

Run actions in an outer context.

This can be used to provide interoperation with base functionality like Control.Exception.catch:

liftWith $  ctx hdl -> catch (hdl (m <$ ctx)) (hdl . (<$ ctx) . h)

The higher-order function takes both an initial context, and a handler phrased as the same sort of distributive law as described in the documentation for thread. This handler takes actions lifted into a context functor, which can be either the initial context, or the derived context produced by handling a previous action.

As with MonadBaseControl, care must be taken when lifting functions like Control.Exception.finally which don’t use the return value of one of their actions, as this can lead to dropped effects.

Since: 1.0.0.0

Re-exports

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

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

Defined in Control.Algebra

Methods

alg :: Choose NonEmpty a -> NonEmpty a

Algebra Empty Maybe

Defined in Control.Algebra

Methods

alg :: Empty Maybe a -> Maybe a

Algebra NonDet []

Defined in Control.Algebra

Methods

alg :: NonDet [] a -> [a]

Algebra sig m => Algebra sig (Alt m)

This instance permits effectful actions to be lifted into the Alt monad, which eases the invocation of repeated alternation with <|>:

a <|> b <|> c <|> d

is equivalent to

getAlt (mconcat [a, b, c, d])

Since: 1.0.1.0

Defined in Control.Algebra

Methods

alg :: sig (Alt m) a -> Alt m a

Algebra sig m => Algebra sig (Ap m)

This instance permits effectful actions to be lifted into the Ap monad given a monoidal return type, which can provide clarity when chaining calls to mappend.

mappend <$> act1 <*> (mappend <$> act2 <*> act3)

is equivalent to

getAp (act1 <> act2 <> act3)

Since: 1.0.1.0

Defined in Control.Algebra

Methods

alg :: sig (Ap m) a -> Ap m a

Algebra sig m => Algebra sig (IdentityT m)

Defined in Control.Algebra

Methods

alg :: sig (IdentityT m) a -> IdentityT m a

Algebra (Lift IO) IO

Defined in Control.Algebra

Methods

alg :: Lift IO IO a -> IO a

Algebra (Lift Identity) Identity

Defined in Control.Algebra

Methods

alg :: Lift Identity Identity a -> Identity a

Monad m => Algebra (Lift m) (LiftC m)

Defined in Control.Carrier.Lift

Methods

alg :: Lift m (LiftC m) a -> LiftC m a

Algebra (Error e) (Either e)

Defined in Control.Algebra

Methods

alg :: Error e (Either e) a -> Either e a

Monoid w => Algebra (Writer w) ((,) w)

Defined in Control.Algebra

Methods

alg :: Writer w ((,) w) a -> (w, a)

Algebra (Reader r) ((->) r :: Type -> Type)

Defined in Control.Algebra

Methods

alg :: Reader r ((->) r) a -> r -> a

(Algebra sig m, Effect sig) => Algebra (Choose :+: sig) (ChooseC m)

Defined in Control.Carrier.Choose.Church

Methods

alg :: (Choose :+: sig) (ChooseC m) a -> ChooseC m a

(Algebra sig m, Effect sig) => Algebra (Empty :+: sig) (EmptyC m)

Defined in Control.Carrier.Empty.Maybe

Methods

alg :: (Empty :+: sig) (EmptyC m) a -> EmptyC m a

(Algebra sig m, Effect sig) => Algebra (NonDet :+: sig) (NonDetC m)

Defined in Control.Carrier.NonDet.Church

Methods

alg :: (NonDet :+: sig) (NonDetC m) a -> NonDetC m a

(MonadIO m, Algebra sig m) => Algebra (Trace :+: sig) (TraceC m)

Defined in Control.Carrier.Trace.Printing

Methods

alg :: (Trace :+: sig) (TraceC m) a -> TraceC m a

Algebra sig m => Algebra (Trace :+: sig) (TraceC m)

Defined in Control.Carrier.Trace.Ignoring

Methods

alg :: (Trace :+: sig) (TraceC m) a -> TraceC m a

(Algebra sig m, Effect sig) => Algebra (Trace :+: sig) (TraceC m)

Defined in Control.Carrier.Trace.Returning

Methods

alg :: (Trace :+: sig) (TraceC m) a -> TraceC m a

(Algebra sig m, Effect sig) => Algebra (Fail :+: sig) (FailC m)

Defined in Control.Carrier.Fail.Either

Methods

alg :: (Fail :+: sig) (FailC m) a -> FailC m a

(Algebra sig m, Effect sig) => Algebra (Fresh :+: sig) (FreshC m)

Defined in Control.Carrier.Fresh.Strict

Methods

alg :: (Fresh :+: sig) (FreshC m) a -> FreshC m a

(Algebra sig m, Effect sig) => Algebra (Cut :+: (NonDet :+: sig)) (CutC m)

Defined in Control.Carrier.Cut.Church

Methods

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

(Algebra sig m, Effect sig) => Algebra (Cull :+: (NonDet :+: sig)) (CullC m)

Defined in Control.Carrier.Cull.Church

Methods

alg :: (Cull :+: (NonDet :+: sig)) (CullC m) a -> CullC m a

Algebra sig m => Algebra (Reader r :+: sig) (ReaderT r m)

Defined in Control.Algebra

Methods

alg :: (Reader r :+: sig) (ReaderT r m) a -> ReaderT r m a

Algebra sig m => Algebra (Reader r :+: sig) (ReaderC r m)

Defined in Control.Carrier.Reader

Methods

alg :: (Reader r :+: sig) (ReaderC r m) a -> ReaderC r m a

(Algebra sig m, Effect sig) => Algebra (State s :+: sig) (StateT s m)

Defined in Control.Algebra

Methods

alg :: (State s :+: sig) (StateT s m) a -> StateT s m a

(Algebra sig m, Effect sig) => Algebra (State s :+: sig) (StateT s m)

Defined in Control.Algebra

Methods

alg :: (State s :+: sig) (StateT s m) a -> StateT s m a

(Algebra sig m, Effect sig) => Algebra (State s :+: sig) (StateC s m)

Defined in Control.Carrier.State.Strict

Methods

alg :: (State s :+: sig) (StateC s m) a -> StateC s m a

(Algebra sig m, Effect sig) => Algebra (State s :+: sig) (StateC s m)

Defined in Control.Carrier.State.Lazy

Methods

alg :: (State s :+: sig) (StateC s m) a -> StateC s m a

(Algebra sig m, Effect sig) => Algebra (Throw e :+: sig) (ThrowC e m)

Defined in Control.Carrier.Throw.Either

Methods

alg :: (Throw e :+: sig) (ThrowC e m) a -> ThrowC e m a

(Algebra sig m, Effect sig) => Algebra (Error e :+: sig) (ExceptT e m)

Defined in Control.Algebra

Methods

alg :: (Error e :+: sig) (ExceptT e m) a -> ExceptT e m a

(Algebra sig m, Effect sig) => Algebra (Error e :+: sig) (ErrorC e m)

Defined in Control.Carrier.Error.Either

Methods

alg :: (Error e :+: sig) (ErrorC e m) a -> ErrorC e m a

(Algebra sig m, Effect sig, Monoid w) => Algebra (Writer w :+: sig) (WriterT w m)

Defined in Control.Algebra

Methods

alg :: (Writer w :+: sig) (WriterT w m) a -> WriterT w m a

(Algebra sig m, Effect sig, Monoid w) => Algebra (Writer w :+: sig) (WriterT w m)

Defined in Control.Algebra

Methods

alg :: (Writer w :+: sig) (WriterT w m) a -> WriterT w m a

(Monoid w, Algebra sig m, Effect sig) => Algebra (Writer w :+: sig) (WriterC w m)

Defined in Control.Carrier.Writer.Strict

Methods

alg :: (Writer w :+: sig) (WriterC w m) a -> WriterC w m a

(HFunctor eff, HFunctor sig, Reifies s (Handler eff m), Monad m, Algebra sig m) => Algebra (eff :+: sig) (InterpretC s eff m)

Defined in Control.Carrier.Interpret

Methods

alg :: (eff :+: sig) (InterpretC s eff m) a -> InterpretC s eff m a

(Algebra sig m, Effect sig, Monoid w) => Algebra (Reader r :+: (Writer w :+: (State s :+: sig))) (RWST r w s m)

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

(Algebra sig m, Effect sig, Monoid w) => Algebra (Reader r :+: (Writer w :+: (State s :+: sig))) (RWST r w s m)

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

class HFunctor sig => Effect sig

The class of effect types, which must:

1. Be functorial in their last two arguments, and
2. Support threading effects in higher-order positions through using the carrier’s suspended context.

All first-order effects (those without existential occurrences of m) admit a default definition of thread provided a Generic1 instance is available for the effect.

Since: 1.0.0.0

Instances

Effect Choose

Defined in Control.Effect.Choose.Internal

Methods

thread :: (Functor ctx, Monad m) => ctx () -> (forall x. ctx (m x) -> n (ctx x)) -> Choose m a -> Choose n (ctx a)

Effect Empty

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)

Effect Trace

Defined in Control.Effect.Trace

Methods

thread :: (Functor ctx, Monad m) => ctx () -> (forall x. ctx (m x) -> n (ctx x)) -> Trace m a -> Trace n (ctx a)

Effect Fresh

Defined in Control.Effect.Fresh

Methods

thread :: (Functor ctx, Monad m) => ctx () -> (forall x. ctx (m x) -> n (ctx x)) -> Fresh m a -> Fresh n (ctx a)

Effect Cut

Defined in Control.Effect.Cut

Methods

thread :: (Functor ctx, Monad m) => ctx () -> (forall x. ctx (m x) -> n (ctx x)) -> Cut m a -> Cut n (ctx a)

Effect Cull

Defined in Control.Effect.Cull

Methods

thread :: (Functor ctx, Monad m) => ctx () -> (forall x. ctx (m x) -> n (ctx x)) -> Cull m a -> Cull n (ctx a)

Effect (Catch e)

Defined in Control.Effect.Catch.Internal

Methods

thread :: (Functor ctx, Monad m) => ctx () -> (forall x. ctx (m x) -> n (ctx x)) -> Catch e m a -> Catch e n (ctx a)

Functor sig => Effect (Lift sig)

Defined in Control.Effect.Lift.Internal

Methods

thread :: (Functor ctx, Monad m) => ctx () -> (forall x. ctx (m x) -> n (ctx x)) -> Lift sig m a -> Lift sig n (ctx a)

Effect (Reader r)

Defined in Control.Effect.Reader.Internal

Methods

thread :: (Functor ctx, Monad m) => ctx () -> (forall x. ctx (m x) -> n (ctx x)) -> Reader r m a -> Reader r n (ctx a)

Effect (State s)

Defined in Control.Effect.State.Internal

Methods

thread :: (Functor ctx, Monad m) => ctx () -> (forall x. ctx (m x) -> n (ctx x)) -> State s m a -> State s n (ctx a)

Effect (Throw e)

Defined in Control.Effect.Throw.Internal

Methods

thread :: (Functor ctx, Monad m) => ctx () -> (forall x. ctx (m x) -> n (ctx x)) -> Throw e m a -> Throw e n (ctx a)

Effect (Writer w)

Defined in Control.Effect.Writer.Internal

Methods

thread :: (Functor ctx, Monad m) => ctx () -> (forall x. ctx (m x) -> n (ctx x)) -> Writer w m a -> Writer w n (ctx a)

(Effect f, Effect g) => Effect (f :+: g)

Defined in Control.Effect.Sum

Methods

thread :: (Functor ctx, Monad m) => ctx () -> (forall x. ctx (m x) -> n (ctx x)) -> (f :+: g) m a -> (f :+: g) n (ctx a)

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

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:

1. Due to a problem with recursive type families, this can lead to significantly slower compiles.
2. 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

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

Since: 1.0.0.0