Effectful.Labeled

Labeled effects.

Example

An effect can be assigned multiple labels and you can have all of them available at the same time.

>>> import Effectful.Reader.Static

>>> :{
 action
   :: ( Labeled "a" (Reader String) :> es
      , Labeled "b" (Reader String) :> es
      , Reader String :> es
      )
   => Eff es String
 action = do
   a <- labeled @"b" @(Reader String) $ do
     labeled @"a" @(Reader String) $ do
       ask
   b <- labeled @"b" @(Reader String) $ do
     ask
   pure $ a ++ b
:}

>>> :{
 runPureEff @String
   . runLabeled @"a" (runReader "a")
   . runLabeled @"b" (runReader "b")
   . runReader "c"
   $ action
:}
"ab"

Effect

data Labeled (label :: k) (e :: Effect) :: Effect

Assign a label to an effect.

Instances

type DispatchOf (Labeled label e)

Defined in Effectful.Labeled

type DispatchOf (Labeled label e) = 'Static 'NoSideEffects

data StaticRep (Labeled label e)

Defined in Effectful.Labeled

data StaticRep (Labeled label e)

Handlers

runLabeled

Arguments

:: forall label e es a b. (Eff (e ': es) a -> Eff es b)

The effect handler.

-> Eff (Labeled label e ': es) a

-> Eff es b

Run a Labeled effect with a given effect handler.

Operations

labeled

Arguments

:: forall label e es a. Labeled label e :> es

=> Eff (e ': es) a

The action using the effect.

-> Eff es a

Bring an effect into scope to be able to run its operations.