Re: [boost] challenge: stable_vector

From: David Abrahams (david.abrahams_at_[hidden])
Date: 2001-07-11 14:57:41

Doesn't work, I think:

template <class Container, class Iterator>
void test_stability(Container& c, Iterator x)
{
    Iterator y = x;
    ++y;
    std::iterator_traits<Iterator>::pointer p = &*y;
    std::iterator_traits<Iterator>::value_type v = *y;
    c.erase(x);
    assert(p == &*y); // test pointer and iterator stability
}

-Dave

----- Original Message -----
From: "Ullrich Koethe" <u.koethe_at_[hidden]>
To: <boost_at_[hidden]>
Sent: Wednesday, July 11, 2001 3:36 PM
Subject: Re: [boost] challenge: stable_vector

> Jeremy Siek wrote:
> >
> > Yes, iterator stability would be problematic.
> >
>
> I think, a stable iterator for a sorted vecor could be achieved by means
> of an 'is_dirty()' function, sililar to a cache. ("stable" in the sense
> that it always points to the same element. Stable
> successors/predecessors cannot be guaranteed.):
>
> /* untested code */
> template <class SortedVector>
> class sorted_vector_iterator
> {
>     SortedVector & its_vector;
>     typename SortedVector::key_type its_key;
>     typename SortedVector::value_type * its_element;
>     typedef typename SortedVector::value_type value_type;
>
>     void update()
>     {
>         if(its_vector.is_dirty())
>         {
>             its_element = &its_vector[its_key]; // or similar
>         }
>     }
>
>     sorted_vector_iterator & operator++()
>     {
>         update();
>         its_element++;  // or similar
>         return *this;
>     }
>
>     value_type operator*()
>     {
>         update();
>         return *its_element;
>     }
> };
>
> Am I missing something?
>
> Ulli
> --
>  ________________________________________________________________
> |                                                                |
> | Ullrich Koethe  Universität Hamburg / University of Hamburg    |
> |                 FB Informatik / Dept. of Computer Science      |
> |                 AB Kognitive Systeme / Cognitive Systems Group |
> |                                                                |
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