Re: [Haskell-cafe] parsec 3 & parsec 2

On Thu, 2008-10-09 at 06:15 +0200, Alfonso Acosta wrote:

ghc-pkg hide {pkg-id}

This will only make a difference to ghc --make. It makes no difference to anything built using Cabal.

On Thu, Oct 9, 2008 at 5:53 AM, Jason Dusek wrote:

...

I don't know anything about how to do that. Is this a Cabal thing? A GHC package registration thing?

Here's the plan: cabal-install can now apply soft package version preferences. There will be a standard set of package version preferences in the hackage index. The initial global soft version preferences will probably be: base < 4 parsec < 3 HaXml == 1.13.* Soft preferences only apply when there is otherwise a free choice. They do not override constraints specified by packages or by the user. cabal-install will use these preferences for the "cabal install" command, but not for "cabal configure". The "install" command uses a constraint solving algorithm to find a consistent installation plan while the "configure" command still just picks the highest version of each package (like ghc --make does). What it means is that things should work when using "cabal install", but you may need to specify version constraints when using ghc --make, runghc Setup or cabal configure. We're currently testing this stuff and setting up a wiki page to explain the details. Note, if you're testing ghc-6.10 and want to use cabal-install then you need to use the very latest version from darcs as it contains some important changes to the dependency resolver. The changes enable it to work with ghc-6.10 which includes two versions of the base library. Very often both versions of the base library need to be used within a single installation plan. The previous resolver could not cope with that (indeed it was specifically designed to avoid that situation normally). Duncan