On 1/29/13 5:58 AM, Gottlob Frege wrote:
How do I know if is it singular valued?
How do you know if an iterator is singular valued? You can't. Same here.
it == container.end()?
Or am I confused?
Nope. A singular valued iterator may not be compared. A singular valued iterator is not associated with any sequence. E.g default constructed iterator pointing to nowhere.
Regards, Why impose the same limitation on recursive_wrapper<T>. Just because
On 01/28/13 16:12, Joel de Guzman wrote: the current variant visitor requires the recursive_wrapper<T> to be dereferenced doesn't mean that's the best practice. Why not, as suggested previously, the visitor protocol allow: operator()(recursive_wrapper<T>const&) and, for that matter have get<T> return a recursive_wrapper<T>& or recursive_wrapper<T>const&. The current variant doesn't do that for, I guess, convenience reasons; however, as evidenced by the current *long* discussion, that convenience is illusory, IMHO. Such a proposal was made previously here: http://lists.boost.org/Archives/boost/2013/01/200407.php but, for some reason, didn't have any responses.