Moduleeffectful-core-2.7.1.2GHC2021

Effectful.Labeled.Writer

Convenience functions for the Labeled Writer effect.

2 types
7 values

Packageeffectful-core-2.7.1.2
Exports9
LanguageGHC2021
LicenceBSD-3-Clause
SourceWriter.hs

Effect

1 declaration

datadata Writer w (a :: Type -> Type) b where

Provide access to a write only value of type w.

Constructors

Tell :: w -> Writer w a ()
Listen :: m a -> Writer w a (a, w)

Instances1DispatchOf

type DispatchOf (Writer w) = 'DynamicDefined in effectful-core-2.7.1.2 · Effectful.Internal.Effect.Dynamic

Handlers

Local

valuerunWriterLocal

:: (HasCallStack, Monoid w)
=> Eff (Labeled label (Writer w) ': es) a
-> Eff es (a, w)

Run the Writer effect and return the final value along with the final output (via Effectful.Writer.Static.Local).

valueexecWriterLocal

:: (HasCallStack, Monoid w)
=> Eff (Labeled label (Writer w) ': es) a
-> Eff es w

Run a Writer effect and return the final output, discarding the final value (via Effectful.Writer.Static.Local).

Shared

valuerunWriterShared

:: (HasCallStack, Monoid w)
=> Eff (Labeled label (Writer w) ': es) a
-> Eff es (a, w)

Run the Writer effect and return the final value along with the final output (via Effectful.Writer.Static.Shared).

valueexecWriterShared

:: (HasCallStack, Monoid w)
=> Eff (Labeled label (Writer w) ': es) a
-> Eff es w

Run the Writer effect and return the final output, discarding the final value (via Effectful.Writer.Static.Shared).

Operations

3 declarations

valuetell :: (HasCallStack, Labeled label (Writer w) :> es) => w -> Eff es ()

Append the given output to the overall output of the Writer.

valuelisten

:: (HasCallStack, Labeled label (Writer w) :> es)
=> Eff es a
-> Eff es (a, w)

Execute an action and append its output to the overall output of the Writer.

valuelistens

:: (HasCallStack, Labeled label (Writer w) :> es)
=> w -> b
-> Eff es a
-> Eff es (a, b)

Execute an action and append its output to the overall output of the Writer, then return the final value along with a function of the recorded output.

listens f m ≡ second f <$> listen m

Re-exports

1 declaration

newtypenewtype Labeled (label :: k) (e :: Effect) (a :: Type -> Type) b where

Assign a label to an effect.

Note: labeled effects are best used together with the effectful-plugin package, as it significantly improves their usability.

The constructor is for sending labeled operations of a dynamically dispatched effect to the handler:

Example1 expression

>>> import Effectful.Dispatch.Dynamic

Example1 expression

>>> :{  data X :: Effect where    X :: X m Int  type instance DispatchOf X = Dynamic:}

Example1 expression

>>> :{  runPureEff . runLabeled @"x" (interpret_ $ \X -> pure 333) $ do    send $ Labeled @"x" X:}333

Constructors

Labeled :: e m a -> Labeled label e a b

Instances2DispatchOf, StaticRep

type DispatchOf (Labeled label e) = DispatchOf eDefined in effectful-core-2.7.1.2 · Effectful.Labeled
data StaticRep (Labeled label e)Defined in effectful-core-2.7.1.2 · Effectful.Labeled