On Sun, 4 Jan 2009, Ross Paterson wrote:
I agree. I had a go at such a restructuring of mtl a while ago:
http://darcs.haskell.org/packages/transformers/ http://darcs.haskell.org/packages/mtl-split/
I wondered, where the packages were gone ...
The first is a Haskell 98 package that defines the monad transformers, operations and liftings, like the mtl-data suggestion. The second adds the FD-based classes. It's close to complete compatibility with mtl, except that State is a synonym for StateT Identity etc. The main problem was haddock's limitations with inter-package re-exports.
What is the current state, since Haddock has moved to GHC-API? At least 'transformers' seems to be distinct enough from current MTL and simple enough to be uploaded to Hackage right now. However, Control.Monad.Identity would conflict with MTL. Without that, 'transformers' could be even used together with the current MTL.