on Thu Sep 29 2011, Krzysztof Żelechowski
Dave Abrahams wrote:
on Wed Sep 28 2011, Nathan Ridge
wrote: 2. The concept mechanism used by Boost should not require singular iterators to exist; the standard is obnoxious and misguided here and promotes sloppy coding.
I think the Boost authors are unlikely to decide to ignore a part of the standard just because one person believes it is obnoxious and misguided and promotes sloppy coding.
I would suggest making your case about the default constructibility of forward iterators at comp.std.c++. If you gain consensus there that this requirement is indeed misguided, then your request will carry more weight here.
I'd also like to point out that there's no rule saying default-constructed iterators must be singular.
A default-constructed iterator must be singular not because the government says so but because of logic.
No. Well, we have to say what we mean by "is singular." Because the concept "singular" only contains two operations (assign and destroy), every valid iterator is-a singular iterator in some sense. But I suspect you mean "minimally singular," and there's no reason at all that a default-constructed iterator need be minimally singular. You usually can't make it usefully dereferenceable (would you want to?) but you can make it copyable, for example. A wrapper over a plain pointer could initialize the pointer to 0. Now it's a valid past-the-end iterator into an array of length zero. Such an iterator is also comparable with other iterators into the same sequence. That's actually far from being minimally singular. -- Dave Abrahams BoostPro Computing http://www.boostpro.com