Re: [jamboost] Re: target references

From: Vladimir Prus (ghost_at_[hidden])
Date: 2004-07-12 11:01:49

David Abrahams wrote:

> > When in foo/bar/baz/Jamfile,
> >
> > ..
> >
> > means "foo/bar", and if there's no Jamfile there, then "..//fu" is not
> > correct, and ../..//fu should be used.
>
> So... the part before the // always refers to a path in the
> filesystem?

No, see below.

> >> > ...or maybe we just need a very clear and complete description of
> >> > these syntaxes in the documentation. It's possible that the reason
> >> > I'm confused is that I've never seen the rules written down.
> >
> > I'll try to write down the rules:
> >
> > 1. The target-id with "//" in it refers to a target in some project. The
> > part before "//" identifies the project, and can be either path to the
> > directory where Jamfile for the other project is placed, or a symbolic
> > id, matching those in 'project' rule for the referred project.
>
> Ack! That's really strange. If I use .. in the path before // it
> _always_ means "up a directory", but other path elements before // may
> be referring to project structure _or_ filesystem structure?
>
> I want to be able to name "boost" symbolically and then refer to
> subprojects relatively. Can I do that?

Ah... I understand what you mean. No... the symbolic project id is always 
absolute: 
/boost
/boost/date_time

or something like that. If you're in /boost/date_time, then you can't refer 
to /boost by using ".." -- this is feature idea which never occured to me.

> > The part after "//" is the
> > name of main target in the referred project.
> >
> > 2. The target-id without "//" either refers to a project (using the rules
> > above), or to a file. We first check if a project by this name exists,
> > and if not, try interpreting the target id as name of the file.
>
> So in that case when checking for a matching project you assume that
> only the last element in such a path names the target
> (i.e. effectively replacing the final '/' with "//")?

I'm not sure I understand. When looking up

/boost/date_time

in

stage dt : /boost/date_time ;

we first check if symbolic name /boost/date_time is known. If not, we try 
looking at *directory* /boost/date_time and check if there's Jamfile in that 
directory.

> > 3. A target id which refers to target in Jamfile, not file, may specify
> > additional properties in the end. All properties should include feature
> > name, so the beginning of property list is identified by "/<"
>
> So far I am not suprised that I was confused. These rules are almost
> impossible to explain coherently.

Hopefully, we can improve them.

- Volodya