Effectful.Labeled.Writer

Convenience functions for the Labeled Writer effect.

Since: 2.4.0.0

Effect

data Writer w :: Effect where

Provide access to a write only value of type w.

Constructors

Tell :: w -> Writer w m ()

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

Instances

type DispatchOf (Writer w)

Defined in Effectful.Writer.Dynamic

type DispatchOf (Writer w) = 'Dynamic

Handlers

Local

runWriterLocal :: forall label w es a. (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).

execWriterLocal :: forall label w es a. (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

runWriterShared :: forall label w es a. (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).

execWriterShared :: forall label w es a. (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

tell :: forall label w es. (HasCallStack, Labeled label (Writer w) :> es) => w -> Eff es ()

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

listen :: forall label w es a. (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.

listens :: forall label w es a b. (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