Re: [Boost-users] [iterators] NULL pointer initialization and comparison using iterator_facade

From: Lang Stefan (SLang_at_[hidden])
Date: 2008-04-24 04:06:11

> >
> > Is it possible to construct metafunctions that allow a 
> function argument
> > of NULL, but not any other integer value? Or at least cause 
> the compiler
> > to call out whenever a non-NULL argument is provided?
> >
> > Cheers,
> > Stefan
> 
> struct convertible_from_null {
>     struct null_pointer_impl_t;
>     typedef null_pointer_impl_t 
> (convertible_from_null::*null_pointer_t)();
>     convertible_from_null(null_pointer_t* = 0) {}
> };
> 
> convertible_from_null test = 0;
> 
> //convertible_from_null fail = 1;
> 
> int main() {}
> 
> In Christ,
> Steven Watanabe
> 

Thanks a lot, this did it! I also managed to adapt this construct to
provide comparison operators for comparisons with NULL values, so all my
issues have been resolved. :)

So now, apart from direct pointer assignments and delete statements
(which I know need to be fixed anyway) my array iterator mostly behaves
like a pointer. Fortunately, thanks to Steven's suggestion, the compiler
does now show up all the problematic statements.

Cheers,
Stefan