From 6511712307028030337 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,b05362a7d4392b67 X-Google-Attributes: gidf78e5,public X-Google-ArrivalTime: 2001-01-04 16:59:03 PST Path: supernews.google.com!sn-xit-02!supernews.com!news.tele.dk!212.74.64.35!colt.net!dispose.news.demon.net!demon!news.demon.co.uk!demon!mail2news.demon.co.uk!not-for-mail From: James Kuyper Newsgroups: comp.std.c++ Subject: Re: Definition of input iterators Date: Fri, 5 Jan 2001 00:58:43 GMT Organization: Not Enough Approved: Fergus Henderson , moderator of comp.std.c++ Message-ID: <3A53BAA2.BF05E027@wizard.net> References: <3A49DDCC.86CCDD18@oxyware.com> X-Trace: mail2news.demon.co.uk 978656330 mail2news:16870 mail2news mail2news.demon.co.uk X-Complaints-To: abuse@demon.net X-Mail2News-Path: news.demon.net!mulga.cs.mu.oz.au X-Authentication-Warning: mulga.cs.mu.OZ.AU: fjh set sender to devnull@stump.algebra.com using -f X-Robomod: STUMP, ichudov@algebra.com (Igor Chudov) X-Accept-Language: en,de,es,ru MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Lines: 25 Xref: supernews.google.com comp.std.c++:3191 Hubert Matthews wrote: > > I've found what I consider to be a problem with the definition of input > iterators in the Standard. Table 72 states that incrementing an > iterator (using either prefix or postfix ++) may invalidate any copies > of that iterator. This is a problem when implementing operator++(int), > as it must return a copy of the pre-increment value of the iterator > which may now not be dereferenceable because of the increment. You're missing the point - that returned value is the only one that IS dereferenceable. It didn't exist yet at that the time the operator++() was executed, and is therefore not at risk. How that's handled internally by the iterator is up to the creator of the iterator class - it might involve making copies that in user code would be risky - however, all the risk is the creator's responsibility. What table 72 is saying is that the creator is free to invalidate any iterator other than the one that is returned. --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.research.att.com/~austern/csc/faq.html ] [ Note that the FAQ URL has changed! Please update your bookmarks. ]