effin: A Typeable-free implementation of extensible effects

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
  where
    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.

Modules

[Index]

Flags

Manual Flags

Name	Description	Default
mtl	Enable MTL support	Enabled

Use -f <flag> to enable a flag, or -f -<flag> to disable that flag. More info

Downloads

• effin-0.3.0.3.tar.gz [browse] (Cabal source package)
• Package description (as included in the package)

Maintainer's Corner

Package maintainers

• AnthonyVandikas

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