Re: [boost] [foreach] cheap_copy crisis?

From: Eric Niebler (eric_at_[hidden])
Date: 2005-12-03 15:58:38

David Abrahams wrote:
> Eric Niebler <eric_at_[hidden]> writes:
> 
>>
>>Put the overload in an associated namespace of the type. Or for maximum 
>>portability, you could put the overload at global scope.
> 
> 
> Really?  If invoked from within a template, global scope overloads
> won't be found unless an argument is in the global namespace or the
> overloads happen to appear before the point of definition of the
> template.

That was the idea, yes.

> If you want a way to make this portable, consider adding a dummy
> parameter that comes from namespace Boost and asking people to
> overload there (the Ramey trick).

I'm not sure how this helps on compilers that don't do ADL. This is a 
macro. BOOST_FOREACH(foo, bar) will expand to something that makes a 
non-qualified call to boost_foreach_has_cheap_copy *in the context of 
the BOOST_FOREACH invocation*. This could be any context, in any 
namespace. If I want this to work on compilers that don't do ADL, 
requiring people to make their overloads visible at global scope seems 
necessary, but I've likely overlooked something.

-- 
Eric Niebler
Boost Consulting
www.boost-consulting.com