Re: [jamboost] feature.jam: Need help with subfeatures

From: David Abrahams (dave_at_[hidden])
Date: 2002-11-29 18:20:19

Vladimir Prus <ghost_at_[hidden]> writes:

> Dave,
> suppose I have feature "gcc" and subfeature version,
> with values 2.95.2 and 3.2. I think it's reasonable
> to type
>
> bjam gcc-3.2
>
> in the command line. But then, the command line
> parsing code has to tell if "gcc-3.2" is property
> or a target. How can I do that? The 'is-implied-value'
> rule returns false for 'gcc-3.2' and I see no other
> way.

First you have to split the string on '-' boundaries. Then, you can
ask if the first element is-implicit-value. I think that's all you
should be asking about at this level of testing; the rest of the
string comprises subfeatures, and if they're malformed I'd like to see
a message like "3.2 is not a know subfeature of <toolset>gcc" more
than one like "couldn't find target gcc-3.2".

> Another remark: I found the comment on 'extend-subfeature'
> very hard to understand. Especially
>
> "the subvalues are specific to the given value of the feature"
>
> The comment for 'value-string' parameter of 'subfeature' rule
> is much more clear for me.

OK, let me try to improve it.

-- 
David Abrahams
dave_at_[hidden] * http://www.boost-consulting.com
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