darcs patch: GenT monad transformer variant of Gen (QuickCheck 2)

[Isaac Dupree]

Duncan Coutts wrote:
> And one thing about it which concerns me somewhat is that it seems to
> want to remain compatible with old versions of things at the expense of
> taking advantage of new features in the current libraries. That might
> make sense for a package that is independently distributed but not for
> one that is bundled with Haskell implementations and the latest versions
> of all dependent libraries.
> 
> My concrete example is that I submitted patches to make Gen an instance
> of Applicative but was told this wasn't ok since it needed to remain
> compatible with ghc-6.2 or something.
> 
> IMOH, if it's part of the core set of packages it should be ok to depend
> on those packages.

Even though it's part of the core set of packages, it could still be 
upgraded, unlike base (we really do need to work on that one some more) 
which it would be depending on a newer version of.

Personally, I don't see the need for new versions of libraries to stay 
compatible with such old versions of GHC (is there a specific old-ghc 
use case I'm unaware of?).  I wonder if we can find a way to upgrade 
their versions of base once most of the stuff in base can be ripped out 
(and layer libraries on top of the mostly unchanged-from-6.2 GHC.* and 
few other parts of base), so that packages only need some more 
dependencies added (if anyone wants to go to the work of messing with 
6.2's base, that is, and possibly weeding out 
specific-to-newer-ghc-but-only-conditioned-by-__GLASGOW_HASKELL__ parts 
from other once-part-of-base libraries if necessary).


Isaac