effect-handlers: A library for writing extensible algebraic effects and handlers. Similar to extensible-effects but with deep handlers.

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This is an extensible effects library for Haskell taking inspiration from the Eff language http://www.eff-lang.org/.

See these papers for the ideas and theory behind the library:

O. Kammar et al: Handlers in Action! http://homepages.inf.ed.ac.uk/slindley/papers/handlers.pdf
A. Bauer, M. Pretnar: Programming with Algebraic Effects and Handlers http://arxiv.org/abs/1203.1539
O Kiselyov, A Sabry, C Swords: Extensible Effects http://dl.acm.org/citation.cfm?id=2503791

Implementation wise it's most close to extensible-effects http://hackage.haskell.org/package/extensible-effects (also see the Extensible Effects paper) but it implements deep handlers instead of shallow.

import Control.Effects.Cont.Eff
import Control.Effects.Cont.Reader
import Control.Effects.Cont.Exception

program = do
  v <- ask
  if v < 15
  then throw $ show v
  else return (v+1)

run n = runPure . handle exceptionHandler . handle (readerHandler n)

res :: Integer -> Either String Integer
res n = run n program

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Modules

[Index]

Control
- Effects
Data
- Data.Union

Downloads

effect-handlers-0.1.0.8.tar.gz [browse] (Cabal source package)
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edofic, blambda

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Versions [RSS]	0.1.0.0, 0.1.0.1, 0.1.0.2, 0.1.0.3, 0.1.0.4, 0.1.0.5, 0.1.0.6, 0.1.0.7, 0.1.0.8
Dependencies	base (>=4.7 && <5), free (>=4.9 && <5), kan-extensions (>=4.1 && <6), mtl (>=2.1 && <3) [details]
License	MIT
Author	Andraz Bajt, Blaz Repas
Maintainer	Andraz Bajt <andraz@bajt.me>
Category	Control
Home page	https://github.com/edofic/effect-handlers
Bug tracker	https://github.com/edofic/effect-handlers/issues
Uploaded	by edofic at 2016-04-28T15:06:03Z
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Reverse Dependencies	1 direct, 0 indirect [details]
Downloads	7247 total (39 in the last 30 days)
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Status	Docs available [build log] Last success reported on 2016-11-26 [all 1 reports]

Readme for effect-handlers-0.1.0.8

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effect-handlers

This is an extensible effects library for Haskell taking inspiration from the Eff language.

See these papers for the ideas and theory behind the library:

Implementation wise it's most close to extensible-effects (also see the Extensible Effects paper) but it implements deep handlers instead of shallow.

What does this library provide?

There is the Eff monad type and modules for pre-implemented effects.

Exception
IO
Reader
Search
State
Writer

It is easy to define your own effects and combine them.

Example

Most of the types are inferred, you only need to provide enough to tell the compiler how to specialize some effect handlers (e.g. readerHandler).

import Control.Effects.Cont.Eff
import Control.Effects.Cont.Reader
import Control.Effects.Cont.Exception

program = do
  v <- ask
  if v < 15 
  then throw $ show v
  else return (v+1)

run n = runPure 
                 . handle exceptionHandler 
                 . handle (readerHandler n)

res :: Integer -> Either String Integer
res n = run n program

Documentation

Haddock docs are available online