From 5424020296289544049 X-Google-Thread: f78e5,c063db358aabf0d8 X-Google-Attributes: gidf78e5,public X-Google-Language: ENGLISH,ASCII Path: g2news2.google.com!news4.google.com!news.glorb.com!news.alt.net!comp-std-cpp-robomod!not-for-mail From: "Satish" Newsgroups: comp.std.c++ Subject: Re: Integer division specification Date: Wed, 21 Feb 2007 20:45:51 CST Organization: http://groups.google.com Lines: 74 Approved: Fergus Henderson , moderator of comp.std.c++ Message-ID: <1172099129.686532.47280@j27g2000cwj.googlegroups.com> References: <45d8adcb$0$7365$19deed1b@news.inter.NL.net> <1171875476.464948.69200@v45g2000cwv.googlegroups.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 8bit X-Trace: posting.google.com 1172099136 7572 127.0.0.1 (21 Feb 2007 23:05:36 GMT) X-Complaints-To: groups-abuse@google.com NNTP-Posting-Date: Wed, 21 Feb 2007 23:05:36 +0000 (UTC) Return-Path: X-Authentication-Warning: mulga.csse.unimelb.edu.au: fjh set sender to devnull@stump.algebra.com using -f X-Robomod: STUMP, ichudov@algebra.com (Igor Chudov) X-Original-To: std-c++@mailman.ucar.edu Delivered-To: std-c++@mailman.ucar.edu User-Agent: G2/1.0 X-HTTP-UserAgent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 1.1.4322),gzip(gfe),gzip(gfe) X-HTTP-Via: 1.0 defrqcpc13dbkf6 (NetCache NetApp/6.0.4) Complaints-To: groups-abuse@google.com Injection-Info: j27g2000cwj.googlegroups.com; posting-host=129.35.231.16; posting-account=yNlyoQ0AAADLgrnzxV6Ac0DtmnxpN5aO X-Virus-Scanned: amavisd-new at ucar.edu X-Virus-Scanned: amavisd-new at csse.unimelb.edu.au X-MIME-Autoconverted: from quoted-printable to 8bit by mulga.csse.unimelb.edu.au id l1LN5f4P026794 X-Virus-Scanned: amavisd-new at csse.unimelb.edu.au Xref: g2news2.google.com comp.std.c++:5678 On Feb 19, 9:49 am, "James Kanze" wrote: > Maarten Kronenburg wrote: > > "Gennaro Prota" wrote > > > >I was wondering if, as part of the synchronization with C99, the C++ > > > >standard is going to require truncation towards zero for integer > > > >division or continue to allow the same choice as C90. > > > Well, let me please do another attempt at getting a reply. I have a > > > defect report concerning the specification of operator / and the > > > proposed resolution would depend on whether truncation "towards -inf" > > > is allowed or not. > > > It would help everyone, not least the committee which would have to > > > examine the DR, to know the answer to this (if it is already known > > > :-)). > > Of course also I don't know the answer of this, because somewhere in the > > world there may be hardware with a compiler where truncation is not towards > > zero. > > I doubt it. Fortran requires truncation toward zero, and when > the C committee considered the issue, they were unable to find > such hardware. > > > All I know is that at least on x86 the truncation is toward zero. When > > the truncation is toward -inf, then technically the remainder becomes the > > modulo. > > In document N2134, 5.6 [expr.mul], it says "the sign of remainder is > > implementation defined" with footnote 78: "According to work underway ... > > the quotient is always rounded toward zero." > > The problem of course is how to know if there are compilers with hardware > > not truncating toward zero. So the solution may then be to have a list of > > e-mail addresses of compiler vendors who can answer that question for you, > > then you could check all the compiler vendors and ask them personally. When > > they wouldn't respond then at least they had the opportunity to object. > > You can probably suppose that any vendor supporting both C and > C++ will handle division the same way in both languages, and C > requires truncation to zero, so the only vendors you'd really > have ask are those who only support C++, and not C. And I don't > think that there are too many of those. > > At the hardware level, of course, hardware tends to be designed > to make programs run faster. Since most (all?) major languages > except C++ require truncation to zero, it seems a safe bet that > all hardware truncates to zero. > > I suspect that the original decision to truncate to zero in > Fortran was based in fact on what the hardware at the time did. > And that the hardware at that time did whatever was simplest and > fastest. Which makes me think that there probably isn't any > reason for hardware ever to do anything else. > > -- > James Kanze (GABI Software) email:james.ka...@gmail.com > Conseils en informatique orient�e objet/ > Beratung in objektorientierter Datenverarbeitung > 9 place S�mard, 78210 St.-Cyr-l'�cole, France, +33 (0)1 30 23 00 34 > > --- > [ comp.std.c++ is moderated. To submit articles, try just posting with ] > [ your news-reader. If that fails, use mailto:std-...@ncar.ucar.edu ] > [ --- Please see the FAQ before posting. --- ] > [ FAQ:http://www.comeaucomputing.com/csc/faq.html ] If using Intel, check if this document will be helpful. ftp://download.intel.com/design/pentium/manuals/241430.htm --- [ 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.comeaucomputing.com/csc/faq.html ]