On 11/6/10 6:20 AM, Reiner Pope wrote:
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.
Clients of hmatrix-static would have to say
if impl(ghc >= 7.0)
Build-Depends: hmatrix-static == 0.4.*
else
Build-Depends: hmatrix-static == 0.3.*
in order to pull in the right dependency for themselves.
In order to get the behavior you're after, though, is trickier business.
Since every version of GHC ships with a different version of base,
you'll have to make use of that knowledge such that users of ghc-7.0
with base-5 will get hmatrix-static-0.4 whereas users of ghc-6.12 with
base-4 will get hmatrix-static-0.3
--
Live well,
~wren
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