On Tue, 23 Dec 2008, Henning Thielemann wrote:
Nicolas Frisby schrieb:
This mtl instance is in conflict with a usage of shift/reset that I'm porting from ML (Sheard's type-directed partial evaluator).
instance (MonadReader r' m) => MonadReader r' (ContT r m) where local f m = ContT $ \c -> do r <- ask local f (runContT m (local (const r) . c))
I need to remove the "local (const r)" bit. I think this is just a different point in the diverse design space of dynamic binding/delimited control. Since Haskell lacks visibility management for importing instances, I'm forced to duplicate the rest of the ContT code in order to replace this instance with my own.
You may define a newtype, lift all required instances with -XGeneralizedNewtypeDeriving and define your own MonadReader instance.
I have put this on: http://haskell.org/haskellwiki/Multiple_instances