On Tue, Nov 17, 2009 at 09:09:07AM -0500, Edward Kmett wrote:
I like that transformers is Haskell 98 and presents a common core. I think that factoring it out is a laudable goal.
However, my very problem is that monads-fd and monads-tf are mutually incompatible. It fragments the community of monad combinator users even further.
If monads-fd sat in the existing location of mtl or was exported there by an mtl compatibility layer and monads-tf used a different namespace then you would have a clean solution in which both could be used in the same code, because both could be loaded.
The proposal is to make the next version of mtl a near-compatibility layer over monads-fd and transformers; it doesn't involve monads-tf directly. We could just rename all the modules in monads-tf (which aimed to mirror mtl-tf), or perhaps rename the modules in both monads-fd and monads-tf. Perhaps we should trim both packages to just the class modules (the others are re-exports mirroring mtl) and relocate those in the module hierarchy: Control.Monad.Cont.Class Control.Monad.Error.Class Control.Monad.RWS.Class Control.Monad.Reader.Class Control.Monad.State.Class Control.Monad.Writer.Class They both have the same Cont class; it need not be duplicated.