freer-0.2.4.1: Implementation of the Freer Monad

CopyrightAllele Dev 2016
LicenseBSD-3
Maintainerallele.dev@gmail.com
Stabilityexperimental
PortabilityPOSIX
Safe HaskellNone
LanguageHaskell2010

Control.Monad.Freer.Writer

Description

Writer effects, for writing changes to an attached environment.

Using http://okmij.org/ftp/Haskell/extensible/Eff1.hs as a starting point.

Synopsis

Documentation

data Writer o x where Source #

Writer effects - send outputs to an effect environment

Constructors

Writer :: o -> Writer o () 

tell :: Member (Writer o) r => o -> Eff r () Source #

Send a change to the attached environment

runWriter :: Monoid o => Eff (Writer o ': r) a -> Eff r (a, o) Source #

Simple handler for Writer effects