[Haskell-cafe] How to make GHC 6.6 and 6.8 co-exist -- was: First go at reactive programming

Duncan Coutts duncan.coutts at worc.ox.ac.uk
Tue Jan 29 05:27:50 EST 2008

On Tue, 2008-01-29 at 06:15 +0000, Tim Docker wrote:
> stevelihn wrote:
> > In my brief experience with Ocaml's GODI, GODI has a way to specify
> > them in a so-called config package. The install package then reads
> > what it needs from the config package. In perl's CPAN shell, you can
> > specify them in the cpan config file (to some extent).
> >
> > I suggest cabal-install looks into this so that moving from one
> > version to another is indeed painless. 6.8.(1|2) is never the last
> > Haskell version. The fact that Cabal records the 3rd digit version in
> > the path indicates a diligent user has to re-install all the packages
> > on every new 3rd-digit dot release. That is a lot of work!
> I like this idea (and  I suggested it previously :-)
>     http://www.mail-archive.com/haskell-cafe@haskell.org/msg33790.html
> It would also potentially solve problems with win32 versus unix
> installations also. Of course, suggesting is the easy bit...

Could one of you please file a feature request:


It's also related to these tickets which you may like to comment on:
      * http://hackage.haskell.org/trac/hackage/ticket/199 "when
        installing a new version of GHC, there should be a way to
        upgrade my packages"
      * http://hackage.haskell.org/trac/hackage/ticket/216 "need a way
        to specify the foreign libraries a package depends on"

My thoughts on the issue are that we should aim to make installation as
automatic as possible. We don't want users having to enter extra
information when it is not essential.

There are times when we cannot possibly detect where some C lib is
installed however and then we should be able to pass extra linker and
include dirs to cabal. I'd do these as configure flags, since that will
work well for systems like Nix and nearly automatically allow such
things to be specified in cabal-install's configure file, though it'd
need some extra work to allow such things to be specified per-package.


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