new language extensions

[Ian Lynagh]

On Thu, Nov 08, 2007 at 10:42:29PM +0000, Duncan Coutts wrote:
> On Thu, 2007-11-08 at 14:27 +0000, Ian Lynagh wrote:
> > On Wed, Nov 07, 2007 at 09:40:25PM +0000, Duncan Coutts wrote:
> > > Last call for objections or comments.
> > > 
> > > We'd like to get this into Language.Haskell.Extension asap so we can
> > > include it in the Cabal distributed with ghc-6.8.2. Currently there are
> > > packages that compiled fine with Cabal and ghc-6.6.x but not with
> > > ghc-6.8.x because we're missing these new more fine-grained language
> > > extensions.
> > > 
> > > See http://hackage.haskell.org/trac/hackage/ticket/160
> > 
> > I'd much rather see http://hackage.haskell.org/trac/hackage/ticket/147
> > fixed.
> 
> I'd prefer to see this proposal debated properly on this list first.
> 
> Also, do you think that is realistic in the time frame for 6.8.2?

Yes, you just change the type declaration and fix the compilation errors
that result. I've done it before and I don't remember running into any
problems.

> > Then Cabal would work with future GHCs, with new extensions as
> > yet undreamt of, as well.
> 
> > This would provide the mechanism we need; the policy, i.e. what the
> > extension names mean, should be defined somewhere outside of Cabal.
> 
> Ok, but where should they be defined?

Stable extensions (e.g. MultiParamTypeClasses) should be described
somewhere central, perhaps the haskell.org wiki.

New exciting stuff that'll probably have completely different semantics
tomorrow should be described in the GHC manual.


Thanks
Ian