MTL vs Transformers. Any status update?

Duncan Coutts duncan.coutts at
Tue Dec 1 07:47:45 EST 2009

On Mon, 2009-11-30 at 23:50 +0000, Ross Paterson wrote:

> I think the pedagogical issue can be handled in other ways, and that
> making compatibility with the current mtl an overriding requirement
> would be unduly constraining.  In any case there would be no complete
> compatibility, as transformers adds Applicative and Alternative instances,
> and also changes the constraints on Functor instances.

I'd advocate doing it the "best" way, whatever the experts agree that
is. Then we can handle the transition using the tools and procedures

The reason I suggest calling it mtl-2 is not for compatibility but to
make it easier to explain to package authors what we recommend they do.


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