Howard Hinnant wrote:
>
> In article <199811231632.RAA03513@su5bpc.labogeo>,
> Philippe.Couton@sercel.fr (Philippe COUTON) wrote:
>
> > The CD2 Draft describes in section 21.3.3 the basic_string's member function
> > reserve() as follows:
> >
> >   void reserve(size_type res_arg=0);
> >
> > But what is the meaning of the 0 default value for the res_arg argument? What
> > is the significance of telling to a basic_string object than I plan to use a
> > size of 0? I don't see.
>
> This is a "non-binding shrink-to-fit request".

BTW it can't be binding because you can't determine if you
already have the minimum capacity; even if size() < capacity(),
the few remaining bytes might not be available for other
allocations (esp if size() doesn't divide 2/4/8).

--

Valentin Bonnard                mailto:bonnardv@pratique.fr
info about C++/a propos du C++: http://pages.pratique.fr/~bonnardv/


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The CD2 Draft describes in section 21.3.3 the basic_string's member function
reserve() as follows:

  void reserve(size_type res_arg=0);

  The member function reserve() is a directive that informs a basic_string
  object of a planned change in size, so that it can manage the storage
  allocation accordingly. Effects:

I understand that as a hint saying to a basic_string object that I will need
soon a size of at least res_arg.

But what is the meaning of the 0 default value for the res_arg argument? What
is the significance of telling to a basic_string object than I plan to use a
size of 0? I don't see.

If I have a basic_string object s with a size of 20 for example, what is his
state after executing s.reserve()?


Regards,
Philippe Couton


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In article <199811231632.RAA03513@su5bpc.labogeo>,
Philippe.Couton@sercel.fr (Philippe COUTON) wrote:

> The CD2 Draft describes in section 21.3.3 the basic_string's member function
> reserve() as follows:
>
>   void reserve(size_type res_arg=0);
>
> But what is the meaning of the 0 default value for the res_arg argument? What
> is the significance of telling to a basic_string object than I plan to use a
> size of 0? I don't see.

This is a "non-binding shrink-to-fit request".

This wording was introduced after the CD2.

> If I have a basic_string object s with a size of 20 for example, what is his
> state after executing s.reserve()?

Depending on the implementation, it may do nothing, or it may knock your
capacity down to 20 (if it was higher).

-Howard
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