Effectful.Writer.Dynamic

The dynamically dispatched variant of the Writer effect.

Note: unless you plan to change interpretations at runtime, it's recommended to use one of the statically dispatched variants, i.e. Effectful.Writer.Static.Local or Effectful.Writer.Static.Shared.

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 :: (HasCallStack, Monoid w) => Eff (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 :: (HasCallStack, Monoid w) => Eff (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 :: (HasCallStack, Monoid w) => Eff (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 :: (HasCallStack, Monoid w) => Eff (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 :: (HasCallStack, Writer w :> es) => w -> Eff es ()

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

listen :: (HasCallStack, 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 :: (HasCallStack, 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