Re: %prefix with C++ namespaces

[Hans Aberg]

On 2 Oct 2007, at 07:03, Joel E. Denny wrote:

> > > It also occurs to me now that a leading "::" is not completely  
> > > redundant.
> > > The given namespace is used in two ways: for declarations and for
> > > references.  The former needs the splitting we discussed.  I  
> > > think the
> > > latter would use the given namespace unaltered.  In that case,  
> > > the leading
> > > "::" would reference the global namespace absolutely.
> >
> > Perhaps you missed it, but in another post, I compared C++ "::" to  
> > the "/" of
> > UNIX filepaths. When it starts with "::", it is like a UNIX  
> > absolute or full
> > path; otherwise, it is a relative path.
>
> No, I get the analogy.  Did I say something to contradict it?

No. We say the same, I think. :-)

> > > I'm having trouble
> > > imagining important scenarios where this will actually help  
> > > disambiguate a
> > > reference.  However, the C++ compiler would complain in the  
> > > scenario you
> > > describe.
> >
> > As for using a leading "::" for reference, I think that is  
> > admitted - or is my
> > memory failing me? :-)
>
> It's allowed.  My point is that, if the user has wrapped parser.cc in
> another namespace, the compiler will complain about any use of the
> absolute reference because it won't include that outer namespace.

Yes, if there are absolute references. I was only thinking about the  
nested 'namespace ...' wrapping, where the innermost names do not  
contain "::". But if these names are references by a full path  
somewhere, the compiler will generate an error.

> In any case, I just tried wrapping parser.cc in a namespace, and it  
> looks
> like there are many other compilation problems the user would have  
> to work
> around anyway, so this issue is probably moot.

Yes, I think
  namespace <name> { ... #include "parser.cc" ... }
invites problems. So that something not to be officially supported by  
Bison, I suspect. :-)

> > I do not think the leading "::"-issue is very important - but it  
> > would be nice
> > showing one has given thought to it. :-)
>
> So, I'm seeing no reason to disallow it.  If the user wants absolute
> references, he should probably get absolute references.

It is OK with me whatever you do. Admitting a leading "::", and  
merely stripping it out in the "namespace" nesting seems fine. It  
seems reasonable enough that more special uses could be considered  
later, if somebody has an input. :-)

  Hans Aberg