Re: [gentoo-portage-dev] Multiple language use, `component-based' design, and other issues

[Jeremy Maitin-Shepard]

Pieter Van den Abeele <pvdabeel@g.o> writes:

> [snip: constraints]

> So if you want to install kde, qt should be installed with option 'kde'
> enabled. But similarily, a component should be able to constrain use flags of
> another package. Or a combination of components could be constrained,
> ...

Ah okay.  I did not consider the addition of such constraints.  If
optional constraints are supported (i.e. pkg1 -> qt(use whatever) OR
something-else(not USE=xaw3d)), the problem becomes quite complex; it
seems it will be non-deterministic polynomial time with respect to the
number of packages in the relevant subset of the dependency graph.

> Reasoning about these things is much much easier in something like prolog. But
> the real advantage here is that prolog can be regarded as a proof engine and
> thus is able to provide a proof why a component with a given specification is in
> a configuration. It is important to ensure that the configuration returned is
> correct and satisfies user constraints/requirements. So in that sense, it will
> be 'provable'. But again, I don't see prolog as an absolute requirement;
> everything which provides the equivalent of a Turing Machine should can be used
> to implement what I'm doing now in Prolog. The set of features that can be
> reused in prolog happens to be bigger than for instance C++ or anything else for
> this problem, which speeds up development of an explicatory prototype.

I see your point here.

-- 
Jeremy Maitin-Shepard

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