Re: [Boost-build] ** Need input on alternative selection **

From: David Abrahams (dave_at_[hidden])
Date: 2007-04-18 02:13:00

on Wed Apr 18 2007, Vladimir Prus <ghost-AT-cs.msu.su> wrote:

> On Sunday 15 April 2007 16:42, David Abrahams wrote:
>> 
>> Volodya and I have been talking about how target alternatives work
>> today in Boost.Build.  We seem to agree that something is wrong with
>> them, but that's about all.  We have different opinions about what's
>> most broken, and therefore different ideas what should be changed. We
>> would appreciate if members of this list help us by expressing their
>> opinions.
>> 
>> You can read my proposal at
>> http://zigzag.cs.msu.su/boost.build/wiki/AlternativeSelection
>
> It appears that our discussion in this thread quickly goes into direction
> of comparing different analogies to the problems discussed. Before we
> get to far, I'd like to revisit some higher-level points. 
>
> Dave, it seems like your proposal has three major aspects:
>
> 1. You claim that using one syntactic elements for both
> requirements and alternative selection is good.

Let's just say it's "not bad," and that it's extremely useful.  I
don't believe anything can be called "bad design" on the basis of
principle alone.  If there are negative consequences of that choice,
that's another matter.

> 2. You claim that it's often desirable to express
> "select this alternative is either <feature1>value1 or ... 
> ... or <featureN>valueN" is in properties.

Yes, especially in the presence of prebuilt libs.

> 3. You claim that alternative selection should consider
> only explicitly specified properties.

Not exactly.  I claim that explicitly specified properties should take
precedence over any property defaults when choosing alternatives.  In
practice that might mean ignoring the defaults altogether, though.

-- 
Dave Abrahams
Boost Consulting
http://www.boost-consulting.com
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