David Abrahams skrev:
on Tue Nov 11 2008, Steven Watanabe <watanabesj-AT-gmail.com> wrote:
AMDG
John Reid wrote:
The following code generates a worrying warning under MSVC:
<snip>
I'm using msvc 8.0 express and boost 1.37.0 release. I've seen similar warnings from gcc 4.3 on similar code. Is this a problem with boost.Multiarray, boost.range or the compiler? My guess is that Multiarray has defined its iterators incorrectly. Can anyone confirm this/provide a fix? This is the result of a bad interaction between iterator_range and iterator_facade.
iterator_facade makes the result of operator[] an rvalue http://www.boost.org/libs/iterator/doc/iterator_facade.html#operator
iterator_range assumes that operator[] for an iterator returns the type reference. http://www.boost.org/libs/range/doc/utility_class.html#iter_range
FWIW, iterator_range is in the wrong here. That is not a safe assumption. It can, however, be checked for fairly reliably at compile-time.
Do you mean that I can detect the return type of operator[] at compile-time and do correct forwarding? If so, how? -Thorsten