Safe Haskell	Safe-Inferred
Language	Haskell2010

Effectful.Writer.Dynamic

Contents

Effect
- Handlers
  - Local
  - Shared
Operations

Description

The dynamically dispatched variant of the Writer effect.

Note: unless you plan to change interpretations at runtime or you need the MonadWriter instance for compatibility with existing code, it's recommended to use one of the statically dispatched variants, i.e. Effectful.Writer.Static.Local or Effectful.Writer.Static.Shared.

Synopsis

data Writer w :: Effect where
- Tell :: w -> Writer w m ()
- Listen :: m a -> Writer w m (a, w)
runWriterLocal :: (HasCallStack, Monoid w) => Eff (Writer w : es) a -> Eff es (a, w)
execWriterLocal :: (HasCallStack, Monoid w) => Eff (Writer w : es) a -> Eff es w
runWriterShared :: (HasCallStack, Monoid w) => Eff (Writer w : es) a -> Eff es (a, w)
execWriterShared :: (HasCallStack, Monoid w) => Eff (Writer w : es) a -> Eff es w
tell :: (HasCallStack, Writer w :> es) => w -> Eff es ()
listen :: (HasCallStack, Writer w :> es) => Eff es a -> Eff es (a, w)
listens :: (HasCallStack, Writer w :> es) => (w -> b) -> Eff es a -> Eff es (a, b)

Effect

data Writer w :: Effect where Source #

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

Instances details

type DispatchOf (Writer w) Source #
Instance details Defined in Effectful.Internal.MTL type DispatchOf (Writer w) = 'Dynamic

Handlers

Local

runWriterLocal :: (HasCallStack, Monoid w) => Eff (Writer w : es) a -> Eff es (a, w) Source #

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 Source #

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) Source #

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 Source #

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 () Source #

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

listen :: (HasCallStack, Writer w :> es) => Eff es a -> Eff es (a, w) Source #

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) Source #

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