[opam-devel] opam install says: Your request cannot be satisfied.

Roberto Di Cosmo roberto at dicosmo.org
Tue Jan 28 15:09:49 GMT 2014

Hi Ashish,
   indeed, when the request is not satisfiable, using the internal solver
or an external one will not change much. The difference only shows up
if the request can be satisfied: in that case, there may be
exponentially many solutions, and the external solvers incorporate
the logic needed to find one that optimises some user criteria.

The long list of constraints that is printed out is actually precious
information that should be helpful in understanding why the request
had no possible solution


On Tue, Jan 28, 2014 at 08:59:41AM -0500, Ashish Agarwal wrote:
> Yes, it prints out a long list of what constraints needed to be satisfied but
> couldn't be. Okay, I was just wondering this for a related question on the Core
> mailing list, which Anil suggested might be solved by using aspcud. It's
> already confirmed that the particular solver didn't help that issue, which
> would also have been clear if I knew that "Your request cannot be satisfied"
> means "provably cannot be satisfied". I'm not suggesting a wording change. I
> think it's fine.
> On Tue, Jan 28, 2014 at 8:45 AM, Thomas Gazagnaire <thomas at gazagnaire.org>
> wrote:
>     > `opam install` says "Your request cannot be satisfied." What exactly does
>     that mean? Has the solver proven that the constraints definitively cannot
>     be satisfied or is there still a possible solution?
>     What else does it prints ? A conflict list ? Yes, it ought to means "there
>     is no solution satisfying the request", but it's possible than the wording
>     is not precise enough.
>     Thomas

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Roberto Di Cosmo
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