Copyright	(c) 2016 Allele Dev; 2017 Ixperta Solutions s.r.o.
License	BSD3
Maintainer	ixcom-core@ixperta.com
Stability	experimental
Portability	GHC specific language extensions.
Safe Haskell	None
Language	Haskell2010

Control.Monad.Freer.StateRW

Description

Composable handler for State effects in terms of Reader and Writer effects. This module is more a tutorial on how to compose handlers. It is slightly slower than a dedicated State handler.

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

Synopsis

Documentation

runStateR :: Eff (Writer s ': (Reader s ': effs)) a -> s -> Eff effs (a, s) Source #

State handler, using Reader and Writer effects.

data Reader e a Source #

Represents shared immutable environment of type (e :: *) which is made available to effectful computation.

data Writer w a Source #

Writer effects - send outputs to an effect environment.

tell :: Member (Writer w) effs => w -> Eff effs () Source #

Send a change to the attached environment.

ask :: Member (Reader e) effs => Eff effs e Source #

Request a value of the environment.