Re: [boost] is_single_element?

From: Victor A. Wagner, Jr. (vawjr_at_[hidden])
Date: 2002-05-17 03:49:34

At Friday 2002/05/17 01:08, you wrote:
>"Victor A. Wagner, Jr." wrote:
> >
> > At Wednesday 2002/05/15 08:45, you wrote:
> >
> > >    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.
>
>I have to read this book. :-( If this is true, you are absolutely right
>to use 'boost::next()'. But why doesn't it work? The only thing I could
>think of is, that 'begin()' returns a 'const iterator&' or something
>like that. Is this allowed? Or is there any other reason?

as I recall (I left the books in the office) you cannot modify a temporary 
of a builtin type, and vector<T>::iterator is almost always implemented as 
T* (a builtin type)... since that's what begin() returns, we're left with 
no way to ++ it.

>Regards, Daniel
>
>--
>Daniel Frey
>
>aixigo AG - financial training, research and technology
>Schloß-Rahe-Straße 15, 52072 Aachen, Germany
>fon: [phone], fax: [phone]
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Victor A. Wagner Jr.      http://rudbek.com
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