Re: About std::vector::resize().

[Martin Sebor <sebor at roguewave dot com>]

Carlo Wood wrote:

> As far as I know this is implementation dependend and using swap
> would be allowed (or so I was told not long ago).
>
> From a practical point of view this seems a very good idea.
> One could implement a resize from size m to size n (n > m) as:
>
> - Create new vector with size n, using the default constructor
>   for all elements.
> - Swap the first m elements.
> - Destroy the old vector.

That's not allowed by 23.2.4.2, p5:

    It is guaranteed that no reallocation takes place during
    insertions that happen after a call to reserve() until the
    time when an insertion would make the size of the vector
    greater than the size specified in the most recent call
    to reserve().

Martin