Re: [boost] challenge: stable_vector

From: Ullrich Koethe (u.koethe_at_[hidden])
Date: 2001-07-11 15:18:50

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    |
|                 FB Informatik / Dept. of Computer Science      |
|                 AB Kognitive Systeme / Cognitive Systems Group |
|                                                                |
| Phone: [phone]                Vogt-Koelln-Str. 30 |
| Fax:   [phone]                D - 22527 Hamburg   |
| Email: u.koethe_at_[hidden]               Germany             |
|        koethe_at_[hidden]                        |
| WWW:   http://kogs-www.informatik.uni-hamburg.de/~koethe/      |
|________________________________________________________________|