From 5746144798939509438 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,66d20309909372f6 X-Google-Attributes: gidf78e5,public From: Oleg Zabluda Subject: Re: STL and set_union algorithm question? (newbie to STL!) Date: 1998/04/12 Message-ID: <6gk4ft$tip@marianna.psu.edu>#1/1 X-Deja-AN: 343281375 Approved: Fergus Henderson References: <6g2te9$a7n$1@ukwsv3.ggr.co.uk> <35290568.2781@wizard.net> <352A9B77.2781E494@pratique.fr> <6gelt5$mpp@marianna.psu.edu> <6gh6t6$ptn@marianna.psu.edu> <352C74D1.3B6F@pratique.fr> X-Original-Date: 9 Apr 1998 23:42:53 -0400 X-Server-Date: 10 Apr 1998 04:35:43 GMT Organization: Penn State University, Center for Academic Computing X-Auth: PGPMoose V1.1 PGP comp.std.c++ iQBFAgUANTCOPuEDnX0m9pzZAQE1aAF5AQti2tfhXlA4T2MWd13yro9IsS4gsCvk MBPr4zH1ZMJOXNCztIUKIx2ptkFVuV39 =Ux5t Reply-To: zabluda@math.psu.edu (Oleg Zabluda) Newsgroups: comp.std.c++ Valentin Bonnard wrote: : Oleg Zabluda wrote: : > I just want it to be non-convertible to set<>::const_iterator. : I understand your opinion. You may also want cont::iterator : not to be convertible to cont::iterator, for any T != U, : which would mean that vector::iterator can't be a pointer. Right. The often used ``typedef T* vector::iterator'' is a disaster, because it does not preclude vector::iterator ==> vector::iterator conversions. However, I wouldn't mind a conversion from cont::iterator to cont::iterator. But since there is no way to express it in C++, I don't wish for it. Note also that the standard does not say that if cont1 and cont2 are different containers, then cont1::iterator must be non-convertible to cont2::iterator (see later). : I think it's should be possible to avoid direct use of primitive : types entirely, but it's too early to impose that given the fact : that using an object (class) instead of a built-in incurs a penalty : under a number of compilers. Well, at least the non-convertability from const_iterator to iterator can be imposed. It's the single largest defect in STL, I know of. STL is a curious part of C++ in this respect. In the rest of the language and stdlib, a lot of work was put into a stronger type system and const correctness. Many old C functions were duplicated to provide const-correct versions. While in STL elementary const-correctness is not mandated. The most notable manifestation of this is the Plauger's library, shipped with MSVC++, where const_iterator's are freely convertible to iterator's for all containers, and it's 100% compliant. To add insult to injury, set::iterator is convertible to map::iterator for all T and U. No kidding. And, again, it's 100% compliant. Oleg. -- Life is a sexually transmitted, 100% lethal disease. --- [ 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 ]