From -8457356854909103204 X-Google-Thread: f78e5,c063db358aabf0d8 X-Google-Attributes: gidf78e5,public X-Google-Language: ENGLISH,ASCII-7-bit Path: g2news2.google.com!news4.google.com!homer!news.glorb.com!news-spur1.glorb.com!news.glorb.com!news.alt.net!comp-std-cpp-robomod!not-for-mail From: "=?iso-8859-1?q?Daniel_Kr=FCgler?=" Newsgroups: comp.std.c++ Subject: Re: Integer division specification Date: Tue, 20 Feb 2007 12:05:32 CST Organization: http://groups.google.com Lines: 70 Approved: Fergus Henderson , moderator of comp.std.c++ Message-ID: <1171810627.755597.115900@v45g2000cwv.googlegroups.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" X-Trace: posting.google.com 1171810633 1642 127.0.0.1 (18 Feb 2007 14:57:13 GMT) X-Complaints-To: groups-abuse@google.com NNTP-Posting-Date: Sun, 18 Feb 2007 14:57:13 +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/5.0 (Windows; U; Windows NT 5.1; de; rv:1.8.1.1) Gecko/20061204 Firefox/2.0.0.1,gzip(gfe),gzip(gfe) Complaints-To: groups-abuse@google.com Injection-Info: v45g2000cwv.googlegroups.com; posting-host=89.48.243.97; posting-account=0YhmiQ0AAABRDjD_6coNmBVB3rgPlaOq X-Virus-Scanned: amavisd-new at ucar.edu X-Virus-Scanned: amavisd-new at csse.unimelb.edu.au X-Virus-Scanned: amavisd-new at csse.unimelb.edu.au Xref: g2news2.google.com comp.std.c++:5647 On 17 Feb., 20:37, Gennaro Prota wrote: > On Wed, 14 Feb 2007 09:25:30 CST, Gennaro Prota wrote: > >Hi, > > >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 > :-)). I'm sorry, that I can be only of limited help here, but even some little help is better than nothing, I guess ;-) I just read the current wording of C99 and the most recent draft for C++. From what I read, I would deduce the following: 1) C99 (More exactly: I have studied 9899:1999 (E) for this), says in 6.5.5/6: "When integers are divided, the result of the / operator is the algebraic quotient with any fractional part discarded.87)" with footnote 87: "This is often called ''truncation toward zero''." so indeed C99 demands truncation toward zero. 2) Opposed to this, N2134 says in 5.6/4: "If both operands are nonnegative then the remainder is nonnegative; if not, the sign of the remainder is implementation-defined78)" with footnote 78: "According to work underway toward the revision of ISO C, the preferred algorithm for integer division follows the rules defined in the ISO Fortran standard, ISO/IEC 1539:1991, in which the quotient is always rounded toward zero." So viewing from the Status Quo I interpret that our C++ Standard does currently would allow any rounding strategy (including truncation "towards -inf") if one of the operands is negative. I cannot say, whether the current state of affairs are by design or not, but the synchronization seems to be useful for most programmers. Greetings from Bremen, Daniel --- [ 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 ]