Re: Why doesn't iter_swap use swap?

[chris jefferson <caj at cs dot york dot ac dot uk>]

Daniel Frey wrote:

> chris wrote:
>
> > Hello,
> >
> > I suspect this might have a simple answer, but why doesn't iter_swap 
> > use swap? I can't see any immediate disadvantages to this, and it 
> > would have the major advantage that any specialisations of swap would 
> > then be used by iter_swap (which is how I discovered the problem, 
> > while trying to overload swap and then wondering why it wasn't 
> > getting used by reverse and other algorithms...)
> >
> > Chris
>
>
> I'm currently discussing the same problem (swap, iter_swap and DR 187) 
> with some Boost folks. While it looks promising at first that 
> iter_swap uses ADL to find specializations, it is also intrusive for 
> the user as he can no longer protect calls from ADL by qualifying 
> them. Also, if a qualified call to iter_swap uses ADL internally, why 
> doesn't a qualified call to swap uses ADL, too? Technically it's 
> possible, Howard Hinnard already tried it out in the Metrowerks STL. 
> We are still undecided whether or not this is a good idea.
However, at least in stdlibc++, almost all uses of iter_swap are written 
std::iter_swap. Therefore at the moment there is no way to user-defined 
overloads, as users can't (or really, really shouldn't) put things in 
std::, and iter_swap doesn't call swap. I think this is a worse situation

Chris