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

From: Thorsten Ottosen (nesotto_at_[hidden])
Date: 2005-09-15 07:48:00

David Abrahams <dave <at> boost-consulting.com> writes:

> 
> Thorsten Ottosen <nesotto <at> cs.aau.dk> writes:
> 

> > then what about the following:
> >
> > Returns:
> >  
> >   x.first         if x is an std::pair
> >   x               if x is an array
> >   range_begin(x)  if range_begin() can be found by ADL
> >   x.begin()       otherwise
> >
> > ?
> 
> that would be an improvement.  I think you need "otherwise," at the
> beginning of all lines of the 2nd column but the first. 

like so

x.first         if x is an std::pair, otherwise
x               if x is an array, otherwise
range_begin(x)  if range_begin() can be found by ADL, otherwise
x.begin()       
 
?

I personally think having one "otherwise" is ok. lot's of math do it like that.

> Nitpicking,
> 
>    range_begin(x)  if range_begin() can be found by ADL
> 
> is not quite right.  I think it's more like
> 
>    range_begin(x) if range_begin(x) is well-formed in an arbitrary
>    namespace.
> 
> but I'm not certain I have that right either. 

hm...what about

  if range_begin() can be found in namespaces associated with
  x.

OTOH, isn't that just ADL?

> Are you really
> detecting whether range_begin can be found via ADL? 

No.

> I wrote code to
> do that trick, but I don't remember seeing it in the range lib.

Cool trick, though.

The suggested spec. says that the return-type depends on 4 cases, it
doesn't state how these cases are implemented. I don't think they need
to state that.

-Thorsten