MTL vs Transformers. Any status update?

Ross Paterson ross at
Thu Nov 26 19:33:02 EST 2009

As I understand it, the Haskell Platform timetable means this will
take some time.

I think the ultimate aim should be that everyone moves to transformers
and monads-fd (probably with some renaming of modules in the latter),
and mtl disappears.  If we decide on that, this is we could get there:

1. rename the modules in monads-fd to their final names.
   (We also need suggestions for what those names should be.)
2. release mtl-2.0 as a deprecated compatibility layer over transformers
   and monads-fd, and get all users to hide all versions of mtl, including
   the new one.   19 packages on hackage must be updated to work with
   the new version.
3. encourage authors to upgrade their packages to depend on transformers
   and (possibly) monads-fd in place of mtl.
4. after a couple of cycles, remove mtl from the platform.

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