Re: [boost] [multi_index] intrusive multi_index poll for interest

From: Joaquín Mª López Muñoz (joaquin_at_[hidden])
Date: 2006-01-19 12:39:10

Bruno Martínez ha escrito:

> On Thu, 19 Jan 2006 06:17:02 -0200, Joaquín Mª López Muñoz
> <joaquin_at_[hidden]> wrote:
>
> > Bruno Martínez ha escrito:
> >
> >> On Sat, 31 Dec 2005 18:01:00 -0200, Maxim Yegorushkin
> >> <maxim.yegorushkin_at_[hidden]> wrote:
> >>
> >> > The most common use cases for intrusive containers are:
> >> >
> >> > * when one would like to store non-copyable elements in a container
> >> > * when it's beneficial to avoid needless data copy in performance
> >> > critical
> >> >    applications
> >>
> >> For me, it's the ability to get an iterator from a pointer.
> >
> > Leaving aside the extra benefits intrusive containers can bring in,
> > the ability of getting an iterator from a pointer to the element is
> > implementable for regular multi_index_containers --matter of fact,
> > this feature is internally used in the preview 1.34 version of
> > Boost.MultiIndex I announced yesterday.
>
> Really? Great!
>
> > * What is the envisioned application scenario for this feature?
>
> I frequently do something like this:
>
> #include <list>
>
> struct part;
>
> struct whole {
>         std::list<part*> parts;
> };
>
> struct part {
>         part(whole& w) : my_whole(&w) {
>                         me = my_whole->parts.insert(my_whole->parts.end(), this);
>         }
>         ~part() {
>                 my_whole->parts.erase(me);
>         }
>         whole* my_whole;
>         std::list<part*>::iterator me;
> };
>

OK, but seems to me the kind of idioms you propose are best served
by an intrusive version of multi_index_container. The "pointer to iterator"
feature does not help in isolation, if I'm understanding you right.

Joaquín M López Muñoz
Telefónica, Investigación y Desarollo