On Wed, Oct 15, 2008 at 5:55 PM, wren ng thornton
Doing it that way removes the polymorphism that MonadState, MonadReader, etc offer to clients. For example, the backwards-state monad[1] is a MonadState but not a StateT (without extra plumbing). There are other examples which don't even change the semantics. It seems a shame to force these implementations to give different names for "the same" functions. Are MPTCs onerous? They'll be in haskell-prime afterall. Of course, the fundeps are another matter entirely...
Slightly off topic - if you do make your backwards-state monad an instance on MonadState be careful not to use Control.Monad.State.Class.modify - executing this falls into a black hole for the backwards-state monad. -Antoine