Re: [boost] Perfect Forwarding (almost)

From: Mat Marcus (mat-boost_at_[hidden])
Date: 2004-02-07 15:26:31

--On Saturday, February 07, 2004 12:59 AM -0500 Brian McNamara 
<lorgon_at_[hidden]> wrote:

> On Fri, Feb 06, 2004 at 07:00:49PM -0500, David Abrahams wrote:
>> The example below shows a technique for perfect forwarding that
>> seems to work with GCC 3.3.1.  rvalues are always moved
>> automatically, and lvalues are copied.
>
> I had to Google for "perfect forwarding" to discover
>    http://std.dkuug.dk/jtc1/sc22/wg21/docs/papers/2002/n1385.htm
>    http://std.dkuug.dk/jtc1/sc22/wg21/docs/papers/2002/n1377.htm
> (which I'd read before but forgotten about).
>
> It is unclear to me if/how your code solves the "perfect forwarding"
> problem.  Instead it appears to show a way to make a particular type
> "movable".  Have I misunderstood?  (How) does your generalize to a
> way to write forwarding functions?
>
> It seems you have a clever way to effectively "detect rvalue-ness";
> the copy-constructor and the "pseudo-copy-constructor" (the thing
> with the enable_if) only swallow lvalues, whereas rvalues find a
> more attractive construction path via "ref".  Is that a correct
> summary?
>
>

[snip]

Some additional background is available here: 
<http://anubis.dkuug.dk/jtc1/sc22/wg21/docs/papers/2002/n1385.htm>

 - Mat