FunctorM.fmapM vs. Traversable with GHC-6.4 and GHC-6.8

[Henning Thielemann]

On Wed, 20 Feb 2008, John Meacham wrote:

> On Thu, Feb 21, 2008 at 05:39:27AM +0100, Henning Thielemann wrote:
> > What is the intended way to make a library using FunctorM/fmapM compatible
> > to both GHC-6.4 and GHC-6.8 ?
>
> Just a note, DrIFT 2.2.3 or later
> (http://repetae.net/computer/haskell/DrIFT/) supports deriving both the
> Foldable and Traversable classes for arbitrary types, this should
> alleviate the migration issues somewhat.

I like a solution like Traversable for GHC-6.4 or FunctorM for GHC-6.8 (as
packages on Hackage).