freer-0.2.3.0: Implementation of the Freer Monad

CopyrightAlej Cabrera 2015
LicenseBSD-3
Maintainercpp.cabrera@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