Re: [Haskell-cafe] Again, version conflicting problem with cabal-install

And today I met another situation, which I think solvable by computer. Hackage A depends on magicloud (any) and container (0.4.0.0), and hackage magicloud depends on container (any). Now I've installed magicloud, using container 0.5.0.0. Then I failed to install A, with any solver. So the solvers are using the status that is installed, not the definitions from original hackages? On Wed, May 2, 2012 at 2:47 PM, Magicloud Magiclouds wrote:

Hi, long time no see. I am using cabal-install-0.15.0. And the new solver. It sure solves some problem. Thanks for the work. Well, on the other hand, there still are hackages that I just have no idea how the author make it (probably not up-to-date hackage database). After human-solver checking, these hackages are not be able to build at all under certain conditions. So, I am voting on the "force-allow" flag.

On Sat, Feb 4, 2012 at 12:36 AM, Andres Löh wrote:

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Hi.

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 --force-allow=foo-1.3

with the semantics that all dependencies on foo will be changed to allow foo-1.3 to be chosen. Would that be ok? Other suggestions?

Can't this be integrated with the current --constraint flag?

It could be, but ...

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If the constraint is able to be satisfied without unrestricting any bounds, fine.  Otherwise, unrestrict any bounds on that constraint.  What would be the drawbacks?

... it shouldn't happen automatically. There are perfectly valid and safe reasons to use --constraint, whereas this new feature is inherently unsafe. But allowing general constraint syntax and calling the flag something with "constraint" in it is perhaps a good idea.

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An advantage is being able to specify --constraint='foo >= 1.3' to get foo-1.3.7.2 instead of having to find out exactly which version you want.  And if you already know what you want, you may always say --constraint='foo == 1.3.7.2'.

Yes.

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Looking forward to the new solver! =)

I need testers and feedback. You can already use it. It's in the cabal-install development version, and can be enabled by saying --solver=modular on the command line.

Cheers,  Andres

-- 竹密岂妨流水过 山高哪阻野云飞

And for G+, please use magiclouds#gmail.com.

-- 竹密岂妨流水过 山高哪阻野云飞 And for G+, please use magiclouds#gmail.com.