[arch-haskell] Adding another data file for dependency "hints"

[Magnus Therning]

On Sat, Jan 1, 2011 at 20:55, Rémy Oudompheng <remyoudompheng at gmail.com> wrote:
> On 2010/12/30 Magnus Therning <magnus at therning.org> wrote:
>> On Tue, Dec 28, 2010 at 09:08, Rémy Oudompheng <remyoudompheng at gmail.com> wrote:
>>> Hello,
>>>
>>> Since pacman's dependency specification is much less powerful than in
>>> Cabal, cabal2arch may output wrong version constraints while trying to
>>> approximate the true specified dependencies. I prefer this to dropping
>>> all version requirements when they cannot be expressed in the pacman's
>>> way.
>>
>> This sounds reasonable.  However, do you have examples of dependencies
>> that CABAL can express but pacman can't?  (I was under the impression
>> that the difference was that CABAL allowed more terse expressions, not
>> that it allowed more.)
>
> See the issue reported by
> https://github.com/archhaskell/cabal2arch/issues#issue/19. PKGBUILDs
> can only specify dependency requirements with one inequality (<, >, <=
> or >=) whereas Cabal can specify any Boolean combination of
> inequalities.

I think it's more correct to say that PKGBUILDS only can specify
conjuctions of dependencies, which does allow it to specify both an
upper and lower bound but not the more complicated dependencies that
CABAL allows.  However, is this really a limitation in practice for
us?  (I do understand that it's a limitation in that it makes it more
difficult to automatically translate dependencies but I see that as a
separate issue.)

>>> In order to get improved PKGBUILDs I thought we could have a better
>>> usage of the dependency resolution capabilities in the Cabal library,
>>> this is summed up in this commit
>>>
>>>  http://github.com/remyoudompheng/archhaskell/commit/2e614b2
>>>
>>> This adds an extra file, platform-provides.txt, that lists our
>>> preferred versions for various packages. For the moment I have filled
>>> it with the contents of Haskell Platform.
>>
>> Is it worth considering downloading this file dynamically, rather than
>> compiling it into the executable statically?
>
> It's been some time since these lists were not compiled in the
> executable. I have added a flag to cabal2arch (in my copy
> http://github.com/remyoudompheng/cabal2arch) to handle a custom
> directory or URL where these files could be stored. I am using mtl for
> error handling.

Why not remove the file from github completely and host it in a
well-known location then?

/M

-- 
Magnus Therning                      OpenPGP: 0xAB4DFBA4
email: magnus at therning.org   jabber: magnus at therning.org
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