From 3417662052975459474 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,7eaa8faac8da5016 X-Google-Attributes: gidf78e5,public From: Valentin Bonnard Subject: Re: Defect Report: member == in container iterators considered harmful Date: 1999/08/17 Message-ID: <37B95B96.7F37@wanadoo.fr>#1/1 X-Deja-AN: 513838652 Content-Transfer-Encoding: 7bit Approved: Valentin Bonnard References: <7p4nj8$n3u@enews4.newsguy.com> X-Original-Date: Tue, 17 Aug 1999 14:54:46 +0200 Content-Type: text/plain; charset=us-ascii Organization: Ecole normale superieure X-Auth: PGPMoose V1.1 PGP comp.std.c++ iQBVAwUAN7mE0qwEuYhIxRhxAQGyXwH/XSUVpeSpfVI0rqurCijvNtdrFT++rGVN HTtiNR1cMmrqcBVWXZegj75yJk8Uyft5cZXU643jGYvWTkVQcmVMNg== =14rt Mime-Version: 1.0 Newsgroups: comp.std.c++ [Note: fowarded to the issue list maintainer] Darin Adler wrote: > Some standard containers define iterator classes to fulfill the requirements > described in 23.1 [lib.container.requirements]. This states that iterator > must be convertible to const_iterator. However, the following code is not > guaranteed to work: > > bool check_equal(std::deque::iterator i, > std::deque::const_iterator ci) > { > return i == ci; > } > > The reason for this is that there's no requirement that the == operator be > defined as a non-member function. It's the contrary: as a non member function, deduction won't ever work. With member functions, it will work sometimes (i == ci is an error, ci == i is ok). So mandating non member functions certainly: - isn't a solution - goes agains the spirit of generic programming -- Valentin Bonnard --- [ 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://reality.sgi.com/austern_mti/std-c++/faq.html ]