On 1/30/13 6:50 AM, Rob Stewart wrote:
On Jan 29, 2013, at 7:04 AM, Joel de Guzman <djowel@gmail.com> wrote:
On 1/29/13 6:56 PM, Rob Stewart wrote:
Singular iterators are default constructed instances that represent a universal end iterator. They are not associated with any particular container, but would be returned by end(), and can be obtained by advancing a non-end iterator far enough.
Singular valued iterators cannot be compared (*). The only valid operations are assignment, destruction and move. There is no way to detect a singular valued iterator.
(* Iterators can also have singular values that are not associated with any sequence. [ Example: After the declaration of an uninitialized pointer x (as with int* x;), x must always be assumed to have a singular value of a pointer. —end example ] Results of most expressions are undefined for singular values; the only exceptions are destroying an iterator that holds a singular value, the assignment of a non-singular value to an iterator that holds a singular value, and, for iterators that satisfy the DefaultConstructible requirements, using a value-initialized iterator as the source of a copy or move operation.)
Oh, sure, slap me down with the standard! :)
Seriously, I was thinking of, for example, std::istream_iterator. If the default constructor doesn't create a singular iterator, what is the right name? I've either forgotten it or long misapplied "singular" to such iterators.
Oh right. Yeah, it will work for std::istream_iterator. In that case, no, it's not "singular valued". I think it's just default contructed, unless I am missing a name too. Some default constructed iterators (e.g. as you pointed out) do not result to being "singular valued". Cheers, -- Joel de Guzman http://www.boostpro.com http://boost-spirit.com