Re: [boost] [range] How to extend Boost.Range?

From: David Abrahams (dave_at_[hidden])
Date: 2005-09-01 09:35:37

"Eric Niebler" <eric_at_[hidden]> writes:

> Pavol Droba wrote:
>
>> Core of the range library is not in the code, rather in concepts that are defined
>> there. 
>> 
>> http://boost.org/libs/range/doc/range.html
>> 
>
>
> In that case, the Range library and the concepts it defines are 
> fundamentally broken. It seems to be requiring that everybody at all 
> times make qualified calls to boost::begin() and boost::end(). 
> Therefore, in order to extend the library, users must put *their* 
> begin() and end() functions in the boost namespace. This is distasteful, 
> but I'll let that slide.

Don't.  It's worse than distasteful: it doesn't work.  

> The more serious problem is the way this interacts with 2-phase
> lookup. 

Right, that's why it doesn't work.  2-phase lookup is in the language,
and anything that doesn't cooperate is broken.

> Since it is a qualified call, any call to boost::begin() from within a 
> template will get resolved during the first lookup phase. If a user's 
> overload has not been seen yet, it will not get considered.
>
> So, is Boost.Range broken, or is this another problem with the 
> documentation?

If Boost.Range is about concepts, those amount to the same thing.

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com