std::string::reserve vs std::vector::reserve

[chris jefferson]

Jonathan Wakely wrote:

> Actually ...
>
>It occurs to me that it is possible that vectors capacity could change
>after an assignment, when we implement move semantics:
>
>    std:vector<int> v;
>    v.reserve(100);
>    v = std::vector<int>();
>
>That would change the capacity, since the temporary would bind to the
>rvalref and the implmenetations would be swapped.  Should we retain the
>old capacity in this case?
>
>e.g.
>
>      vector&
>      operator=(__gnu_cxx::__rvalref<vector> __x)
>      {
>        this->swap(__x.__ref);
>+       this->reserve(__x.capacity());
>        return *this;
>      }
>
>jon
>
>  
>
While I'm not sure it's been properly finalised yet, I believe the plan 
is to leave things that have been moved from in a valid, but unknown 
state (sorry if that isn't the correct legalise). At some point it might 
turn out what I should, or would be better, to do would be to destroy 
the existing vector and just set the vector being moved from as an empty 
vector.

I've been working under the assumption that after something has been 
moved from, the only valid things to do to it are assign to it, move 
assign a new value to it, or destroy it. These are possibly too strong, 
but have the advantage that a) They are I believe the only reasonable 
things anyone would want to do, and b) I'm sure they can be weaker than 
what the final requirements will be :)

At present, any or all of these choices are totally invisable to users 
of course :)

Chris