Re: [Boost-users] Functions that evaluate to constants

From: Ovanes Markarian (om_boost_at_[hidden])
Date: 2008-03-31 13:21:57

Sorry, my current compiler is VC++ 7.1

On Mon, Mar 31, 2008 at 7:21 PM, Ovanes Markarian <om_boost_at_[hidden]>
wrote:

> I would like to refer you to this address:
>
> http://en.wikibooks.org/wiki/More_C%2B%2B_Idioms/nullptr
>
> Is there any chance tha in your tests int* foo is a member variable? Which
> compiler do you use?
>
> The example from the location above compiles fine, except the line:
>
>   const int n = 0;
>   if (nullptr == n) {}        // ok
>
>   Which IMO is a mistake in the wiki page.
>
>
>
> With Kind Regards,
> Ovanes Markarian
>
>
> On Mon, Mar 31, 2008 at 6:57 PM, Robert Dailey <rcdailey_at_[hidden]> wrote:
>
> > Hi,
> >
> > I realize that C++03 will not permit functions to evaluate down to
> > compile-time constants. However, I cannot wait until C++0x for this feature.
> > So, I'm hoping that Boost will allow a temporary solution. Consider the
> > following structure:
> >
> > static struct nullptr_t
> > {
> >     template< typename t_type >
> >     operator t_type*() { return 0; }
> > } nullptr;
> >
> > The compiler has everything it needs to turn this code into a single
> > integral constant value. So, if I do the following:
> >
> > int* foo;
> > if( foo == nullptr )
> > {
> > }
> >
> >
> > Then it should evaluate down to:
> >
> > int* foo;
> > if( foo == 0 )
> > {
> > }
> >
> > Is there any way to provide this behavior in Boost? I would like to
> > avoid altering the actual design if possible. Perhaps this actually *does*
> > evaluate to a constant and the problem is that I'm actually unaware of some
> > specific rule that I didn't find in the C++03 standard. Thanks.
> >
> > _______________________________________________
> > Boost-users mailing list
> > Boost-users_at_[hidden]
> > http://lists.boost.org/mailman/listinfo.cgi/boost-users
> >
>
>