-1 in their current form.

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.

As it is, all that is done is we will go through all the trouble of breaking a lot of existing code, only to have to make a decision about which half of the code we broke we want to break again later once the community slides towards monads-fd or monads-tf or more likely stagnates in indecision between them.

In the meantime there is no right answer for library authors who want to be able to support both.

If this is the direction we want to go, I don't see how we could conscionably make the choice to change without making it so that monads-fd and monads-tf can both be loaded by the same program, lest we find ourselves having this very discussion again in 6 months.

-Edward Kmett

On Tue, Nov 17, 2009 at 7:56 AM, Michael Snoyman <michael@snoyman.com> wrote:


On Tue, Nov 17, 2009 at 10:19 AM, Nicolas Pouillard <nicolas.pouillard@gmail.com> wrote:
Excerpts from Edward Kmett's message of Tue Nov 17 05:03:01 +0100 2009:
> On Mon, Nov 16, 2009 at 8:42 PM, Erik de Castro Lopo
> <mle+hs@mega-nerd.com<mle%2Bhs@mega-nerd.com>
> > wrote:
>
> > Valery V. Vorotyntsev wrote:
> >
> > > Thus, the question is: are there any transformers-specific features
> > > iteratee package needs, or can it just go with mtl?
> >
> > I have successful build iteratee by replacing transformers with
> > mtl in the .cabal file.
> >
> > > I suspect mtl to be more popular... And actual "popularity" can be
> > > measured.
> >
> > Popularity is not the issue. The issue is that we are currently
> > in a transition from using mtl to using transformers. See:
> >
> >   http://www.haskell.org/pipermail/libraries/2009-March/011415.html
> >   http://www.haskell.org/pipermail/haskell-cafe/2009-October/067744.html
> >
> >
> Are we?

Let's make a poll then!

transformers+1

FWIW, +1 transformers. I like being able to swap monads-fd and monads-tf.

Michael