Re: [boost] is_single_element?

From: Victor A. Wagner, Jr. (vawjr_at_[hidden])
Date: 2002-05-17 02:01:21

At Wednesday 2002/05/15 08:45, you wrote:
>Damien Fisher wrote:
> >
> > I would like to see something like this in Boost:
> >
> > template<typename Container>
> > bool is_single_element(const Container &cont)
> > {
> >     return boost::next(cont.begin()) == cont.end();
> > }
> >
> > [...]
> >
> > Comments?
>
>    return !cont.empty() && ++cont.begin() == cont.end();

As Scott Meyers points out in his "Effective STL", ++cont.begin() MAY NOT 
compile, depending on the implementation.  That's a _serious_ drawback, 
IMO.  Slow (for stupid compilers) beats not compiling any day.

>The bug was also mentioned by David and is fixed by the test for
>!empty() and using 'boost::next' is pointless in the given context, it
>might even be slower for stupid compilers. Besides that, the function is
>nice to have. I'd like to see it in next to 'prior' and 'next' (the name
>could need some discussion, but I don't have a better idea).
>
>Regards, Daniel
>
>--
>Daniel Frey
>
>aixigo AG - financial training, research and technology
>Schloß-Rahe-Straße 15, 52072 Aachen, Germany
>fon: [phone], fax: [phone]
>eMail: daniel.frey_at_[hidden], web: http://www.aixigo.de
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Victor A. Wagner Jr.      http://rudbek.com
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