Re: [boost] challenge: stable_vector

From: David Abrahams (david.abrahams_at_[hidden])
Date: 2001-07-11 20:03:11

Ulli,

I just don't see it. Remember that erasing an element of the vector
invalidates all following iterators. Maybe you have something in mind that
you haven't explained?

-Dave

----- Original Message -----
From: "Ullrich Koethe" <u.koethe_at_[hidden]>
To: <boost_at_[hidden]>
Sent: Wednesday, July 11, 2001 4:18 PM
Subject: Re: [boost] challenge: stable_vector

> David Abrahams wrote:
> >
> > 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
> > }
> >
>
> Too bad. But it could be repaired if the vector actually stored
> "pair<key,value>*". The additional indirection could be hidden in the
> access functions. Of course, performance will suffer.
>
> On the other hand,
>
> assert(v.first == (*y).first);
> assert(v.second == (*y).second);
>
> would work, and I regard this as the more important requirement. If the
> mapped object were stored by pointer, even
>
> assert(&v.second == &(*y).second);
>
> would work. I regard the pair stored in a map as as helper object whose
> identity is of no interest.
>
> Ulli
> --
>  ________________________________________________________________
> |                                                                |
> | Ullrich Koethe  Universität Hamburg / University of Hamburg    |
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