[boost] Re: [range] update on ADL hooks

From: Eric Niebler (eric_at_[hidden])
Date: 2005-03-23 20:55:34

Thorsten Ottosen wrote:
> "Eric Niebler" <eric_at_[hidden]> wrote in message 
>  We're talking about the ADL
> | customization points of /one particular library/.
> 
> are we?

Yes, we are.

  The thing is IMO that were are talking about customization
> points of a concept, not a particular library.

No. boost_range_begin() is *only* called from boost::begin(). Nobody 
should be calling it directly. It is part of the Boost.Range library's 
interface that it can be customized this way. Concepts have nothing to 
do with it.

> | A customization point
> | cannot be in two libraries simultaneously. I must have missed your point
> | again. Please set me straight.
> 
> struct Foo
> { ... this is a range with adaptation ... }
> 
> iterator boost_range_begin( Foo& f );
> 
> iterator std_range_begin( Foo& f );
> 
> iterator adope_range_begin( Foo& f );
> 
> what is the difference between the three functions, apart from their name?

Separate libraries should not be picking the same name for use as a 
customization point. The Range library is the only place that defines 
the Range concept, and it has one function, boost::begin(), for finding 
the beginning of the range. That function has one customization point. 
What should it be called? That's the only thing we're concerned with here.

> 
> | But you still haven't given me a reason I can understand why it
> | shouldn't be "boost_range_begin()" etc..
> 
> I'm saying that it might not be the right solution; I don't see
> why we should give the same concept different interfaces.

Concepts are not the concern here -- only how to allow users to 
customize the behavior of a library.

> 
> We are already protecting classes by a namespace, shouldn't that be enough.
> 

No, because we're using unqualified calls to turn on ADL.

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