Re: New New Callbacks Uploaded

From: William Kempf (sirwillard_at_[hidden])
Date: 2000-11-22 15:16:28

--- In boost_at_[hidden], "Peter Dimov" <pdimov_at_m...> wrote:
> From: "William Kempf" <sirwillard_at_m...>
> 
> > As for ref-counting vs. cloning... that's a trickier question.
> 
> Indeed. :-)
> 
> > I'm
> > leaning in favor of ref-counting since a callback is likely to be
> > passed around frequently.
> 
> That's not obvious to me. Why is a callback likely to be passed 
around
> frequently - in performance critical code?

Well, I'm willing to concede that the term "frequently" is a 
misnomer.  I suppose that most general usages of a callback won't 
copy more than a few times at the most.  However, I was considering 
how callbacks could be stored within a container which can cause 
frequent copies to be made.  There's ways around this, though, so 
maybe I need to rethink my position here.

> > However, I'd love to hear a list of pros
> > and cons from people for both strategies just to make sure I've 
not
> > missed any that could change my opinion (and to help others 
formulate
> > their own opinions as well).
> 
> A list of pros and cons won't help, because a cloning callback and a
> reference counted callback are different concepts. Sometimes you'll 
need the
> one, sometimes the other.

This I'm not so sure about.  Yes, their behavior is radically 
different.  However, I find it difficult to think of specific 
situations where one would be the answer while the other would not.  
Can you spark my thinking on this?
 
> One other point that crossed my mind is that building a refcounted 
callback
> on top of a cloning one is (relatively) easy, while the opposite is 
not
> trivial. Assuming the compiler has void returns, of course.

If both are truly useful then I'd agree that the cloning version is 
the more important of the two.

Bill Kempf