On 1/29/13 11:18 AM, Larry Evans wrote:
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:
AFAICT, you can already do that with any smart pointer (e.g. unique_ptr<T>) Regards, -- Joel de Guzman http://www.boostpro.com http://boost-spirit.com