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Re: Sequence container capacity after calling clear()

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On Saturday, March 23, 2013 2:30:03 PM UTC-7, Leigh Johnston wrote:
> Hi,
>
>
>
> Can we please change the ISO C++ Standard so that explicitly states what
>
> happens to a sequence container's capacity() after calling clear()?
>
>
>
> Currently the behaviour is unspecified and I know of at least one
>
> implementation that deallocates on vector<T>::clear().
>
>
>
> If the behaviour remains unspecified then it is effectively impossible
>
> to write portable code that uses clear() and you have to hope things
>
> such as v.erase(v.begin(), v.end()) behave more consistently across
>
> different implementations.

I don't see what's non-portable about this.

If you don't care what the capacity is, you use `clear` and let the
implementation decide. It's not non-portable because your code
*doesn't care*. If you *do* care about the capacity, then you either
want the capacity to be zeroed out or you want it to be preserved. And
you already have the tools to do either:

    vec.resize(0); //Destroys contents, but doesn't change the capacity.
    vec = vector<T>{}; //Destroys contents and reduces the capacity.

Both of these are reasonable behaviors, so the user should be able to
do either if they want a specific result.


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Thread

Sequence container capacity after calling clear() Leigh Johnston <leigh@i42.co.uk> - 2013-03-23 16:27 -0600
  Re: Sequence container capacity after calling clear() Daniel Krügler <daniel.kruegler@googlemail.com> - 2013-03-23 22:05 -0700
    Re: Sequence container capacity after calling clear() James Kanze <james.kanze@googlemail.com> - 2013-03-27 13:28 -0600
  Re: Sequence container capacity after calling clear() Jason McKesson <jmckesson@googlemail.com> - 2013-03-23 22:05 -0700
  Re: Sequence container capacity after calling clear() Juha Nieminen <nospam@thanks.invalid> - 2013-03-24 23:36 -0700
  Re: Sequence container capacity after calling clear() Mathias Gaunard <loufoque@googlemail.com> - 2013-03-25 10:49 -0600
    Re: Sequence container capacity after calling clear() Leigh Johnston <leigh@i42.co.uk> - 2013-03-26 08:55 -0600

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