Re: [Haskell-cafe] Compiler constraints in cabal

I was aware of this condition, but I'm not precisely sure it addresses my requirements. When you run "cabal install some-package", cabal reads all version constraints listed in the "build-depends" field, and chooses which versions of which packages to download from Hackage in order to satisfy these constraints. I want to expose my dependency on a particular version of ghc to cabal's constraint satisfier. The end result I want is that when you type "cabal install hmatrix-static" with ghc-6.12 installed, then cabal chooses hmatrix-static-0.3; and when you type "cabal install hmatrix-static" with ghc-7.0 installed, then cabal chooses hmatrix-static-0.4. As I understand it, using "impl(ghc >= 7.0)" won't achieve this. The closest thing I can think of is to write my hmatrix-static.cabal file for version 0.4 as:

... if impl(ghc < 7.0) build-depends: nonexistant-package ...

so that cabal cannot satisfy the constraints for hmatrix-static-0.4 unless I have ghc >= 7.0. This seems a little hacky, and I'm also not sure if it works. (I'm finding it rather hard to test these ideas, because I don't want to upload a new package to Hackage every time...) All the best, Reiner On 6 November 2010 19:24, wren ng thornton wrote:

On 11/6/10 3:13 AM, Ivan Lazar Miljenovic wrote:

...

On 6 November 2010 17:52, Reiner Pope  wrote:

...

Ah, I hadn't thought of that. But doesn't the version of GHC change much more often than the version of base does?

Each major version of GHC has a different (major) version of base.

I think you can also say stuff like "ghc>= 6.10", but I'm not sure.

The correct condition notation is: impl(ghc >= 6.10)

-- Live well, ~wren _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe