Re: [Boost-users] [Intrusive] List Manipulation and Management

Subject: Re: [Boost-users] [Intrusive] List Manipulation and Management
From: Stefan Strasser (strasser_at_[hidden])
Date: 2009-09-26 19:40:59

Am Sunday 27 September 2009 00:21:52 schrieb Freddie Witherden:
> Hi,
>
> On 26 Sep 2009, at 23:49, Stefan Strasser wrote:
> > list.splice(list.end(),otherlist);
> >
> > boost.intrusive represents the nodes as STL-like containers, if you
> > need to
> > port code that handles nodes directly you might be interested in
> > *list_algorithms of boost.intrusive, but I'd recommend using the
> > containers.
>
> Doesn't splice require otherlist to be a list? This seems to make it
> somewhat inadequate, as the docs make the list class out to be rather
> brittle (non-copyable and non-assignable), so returning a list from
> afunction() is not a option. I guess one can return a pointer to a new-
> ly allocated list, but that is another pointer to delete and more
> boilerplate code.
>
> I would rather use the containers if at all possible, however, the
> design seems to be working against me in this scenario.

you cannot treat intrusive lists as values that you can return, this is by 
concept. a single value(more precicely: hook) can only be part of one 
intrusive list at a time.
there are multiple solutions for this, depending on your code. passing the 
list by reference to the function, passing an back_insert_iterator as 
OutputIterator etc.

see e.g. http://www.cplusplus.com/reference/std/iterator/back_insert_iterator/

>
> >> Secondly, when dealing with heap allocated items, which need to be
> >> deleted, the current code uses a while loop to call each nodes
> >> destructor. What is the intrusive equivalent?
> >
> > clear_and_dispose()
>
> Excellent. In the library I am writing/porting it is sometimes
> necessary to return one of these lists. Naturally, one will want to
> return a clone of the internal list, however, what would be the nicest
> way to ensure its disposal? It may be somewhat haphazard to rely on
> users to call a specific dispose/delete method. Are there any
> exceptionally neat solutions to this?

clear_and_dispose calls a dispose function. but it is user supplied and it is 
possible to remove from the list without disposing, but this is intentional 
again.
depending on your use case again, you could
A *a= new A[1000];
{
  list<...> l;
  l.push_back(a[500]);
  //more list calls
}
delete a;

and not worry about disposing while using the list.