Re: [boost] [range/iterator] operator[] forwarding

From: Thorsten Ottosen (thorsten.ottosen_at_[hidden])
Date: 2006-10-04 04:23:53

Shunsuke Sogame wrote:
> Hi gurus, under RC_1_34,
> 
>     #include <boost/range.hpp>
>     #include <boost/iterator/counting_iterator.hpp>
> 
>     int main()
>     {
>         boost::make_iterator_range(
>             boost::make_counting_iterator(0),
>             boost::make_counting_iterator(5)
>         )[2];
>     }
> 
> 
> VC++7.1 and GCC3.4 says a warning something like
> "returning address of local variable or temporary".

I think counting_iterator is not a valid random access iterator because 
operator[]() does not yield a reference.

> counting_iterator is implemented by iterator_facade,
> whose operator[] returns *value*.
> In fact, the result type of iterator_facade's operator[] seems unspecified.
> Is it possible to do forwarding of iterator's operator[], which is
> tried by iterator_range?

Counting iterator should define its reference-type to be the type it 
returns from operator[]() (even though it is not a reference). Then I 
think it would work.

Do the authors of the iterator lib agree?

-Thorsten