effin: A Typeable-free implementation of extensible effects

[ bsd3, control, effect, library ] [ Propose Tags ]

This package implements extensible effects, an alternative to monad transformers. The original paper can be found at http://okmij.org/ftp/Haskell/extensible/exteff.pdf. The main differences between this library and the one described in the paper are that this library does not use the Typeable type class, does not require that effects implement the Functor type class, and has a simpler API for handling effects.

For example, the following code implements a handler for exceptions:

newtype Exception e = Throw e

runException :: Effect (Exception e :+ es) a -> Effect es (Either e a)
runException = eliminate
    (\x -> return (Right x))
    (\(Throw e) k -> return (Left e))

Compare this to the corresponding code in extensible-effects (http://hackage.haskell.org/package/extensible-effects):

runExc :: Typeable e => Eff (Exc e :> r) a -> Eff r (Either e a)
runExc = loop . admin
    loop (Val x) = return (Right x)
    loop (E u)   = handleRelay u loop (\(Exc e) -> return (Left e))

In particular, effect implementors are not required to do any recursion, thereby making effect handlers more composeable.

Versions [faq],,,,,,,,,,
Dependencies base (>=4.7 && <4.9), mtl (>=2.1 && <3) [details]
License BSD-3-Clause
Copyright (c) 2014 Anthony Vandikas
Author Anthony Vandikas
Maintainer yellpika@gmail.com
Category Control, Effect
Home page https://github.com/YellPika/effin
Source repo head: git clone git://github.com/YellPika/effin.git
Uploaded by AnthonyVandikas at Sat Jul 11 19:59:34 UTC 2015
Distributions NixOS:
Downloads 4994 total (223 in the last 30 days)
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Status Hackage Matrix CI
Docs available [build log]
Last success reported on 2015-07-11 [all 1 reports]





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