Am Samstag, 10. Januar 2009 22:30 schrieb Ross Paterson:
On Sat, Jan 10, 2009 at 10:20:59PM +0100, Henning Thielemann wrote:
What are the changes from transformers-0.0.1.0 to transformers-0.1.0.0 ?
Instances for Applicative and Alternative.
Great! And we should try to make Applicative a superclass of Monad and drop MonadPlus in favor of Alternative + Monad. It would be probably even better to have somethink like Alternative/MonadPlus for functors (since functors are the most general concept at this point) and drop Alternative and MonadPlus (or use the name „Alternative“ for this new class). It’s terrible to explain all this legacy (Applicative not being superclass of Monad, two different classes for monoid functors) to students and to mention Applicative in a class context which already mentions Monad. However, we’ll probably need something like John Meachem’s class alias proposal to make such a transition as smooth as possible. Anyone who wants to hack GHC in this regard? Best wishes, Wolfgang