Re: [boost] Library TR draft available

From: John Maddock (john_at_[hidden])
Date: 2004-11-14 10:54:49

> >In other words I'm suggesting a tr1 subdirectory in the Boost tree
> >containing the tr1 headers, which would either be wrappers to the std or
> >Boost versions as required.
>
> That would seem to cater to both boost users and boost developers, 
> allowing either to specify the boost library always (by simply ignoring 
> the tr1 subtree), or the native tr1 code if available but the boost code 
> otherwise (by #including from the tr1 subtree and using the std::tr1 
> namespace). It works regardless of whether full or partial native tr1 
> implementations are available. It isolates all the messy #ifdefs into the 
> tr1 subtree headers, so regular boost code doesn't have to be littered 
> with tr1 related #ifdefs.
>
> I like it. Will there be serious ADL issues?

I don't know, let me think, we're talking about ADL finding components in 
namespace std::tr1 right?  As long as the function arguments are from the 
same namespace, it doesn't matter what that namespace is actually called 
(boost or std::tr1), unless we have a mixture of code (some really in tr1, 
some in boost), in which case there's probably not much we can do.

More seriously, users cannot specialise templates in namespace std::tr1, 
because that may not be where the declarations really live: this may be an 
issue for type_traits for example.

Even so I would expect the number of gotcha's to be reasonably small, at 
least as a first approximation; using declarations sure beat reimplementing 
everything in another namespace!

> Presumably the tr1 subtree would go in the boost directory?

I don't know, lets see what folks want: whatever this directory would have 
to be in the users include path (as well as the regular boost tree).

John.