{-# LANGUAGE MultiParamTypeClasses, TypeFamilies, FlexibleContexts #-} module Control.Effects.Either where import Control.Effects import Data.Void throwEither :: (c ~ ContT (Either e r) m, AutoLift c n, Monad m) => Proxy c -> e -> n Void throwEither p e = operation p $ \_ -> return $ Left e catchEither :: Monad m => (e -> m a) -> Handler (Either e a) a m a catchEither h = Handler { ret = return . return , fin = either h return }