From -3849035065381660039 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,c4044a0e79c89b37 X-Google-Attributes: gidf78e5,public X-Google-ArrivalTime: 2002-12-27 13:02:36 PST Path: archiver1.google.com!news1.google.com!newsfeed.stanford.edu!logbridge.uoregon.edu!kibo.news.demon.net!mutlu.news.demon.net!demon!mail2news.demon.co.uk!devnull From: nagle@animats.com (John Nagle) Newsgroups: comp.std.c++ Subject: Re: comparing signed and unsigned integral values Date: Fri, 27 Dec 2002 21:02:30 +0000 (UTC) Organization: Prodigy Internet http://www.prodigy.com Lines: 56 Approved: fjh@cs.mu.oz.au (Fergus Henderson , moderator of comp.std.c++) Message-ID: <3E0C04E0.2040708@animats.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Trace: mail2news.demon.co.uk 1041022950 13476 10.0.0.1 (27 Dec 2002 21:02:30 GMT) X-Complaints-To: abuse@demon.net NNTP-Posting-Date: Fri, 27 Dec 2002 21:02:30 +0000 (UTC) X-Received: from mulga.cs.mu.oz.au ([128.250.1.22]) by news.demon.co.uk with esmtp (Exim 4.05) id 18S1ci-0003VD-00 for mail2news@news.news.demon.net; Fri, 27 Dec 2002 21:02:29 +0000 X-Received: by mulga.cs.mu.OZ.AU id IAA26770; Sat, 28 Dec 2002 08:02:21 +1100 (EST) X-Authentication-Warning: mulga.cs.mu.OZ.AU: fjh set sender to devnull@stump.algebra.com using -f X-Path: comp-std-cpp-robomod!not-for-mail X-Robomod: STUMP, ichudov@algebra.com (Igor Chudov) X-Delivered-To: std-c++@ncar.ucar.edu X-User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:0.9.4) Gecko/20011128 Netscape6/6.2.1 X-Accept-Language: en-us X-Newsgroups: comp.std.c++ X-NNTP-Posting-Date: Fri, 27 Dec 2002 02:41:21 EST X-UserInfo1: SCSGW^_D\JUQB\D[NCOF_W\@PJ_^PBQLGPQRZ_MHEQR@ETUCCNSKQFCY@TXDX_WHSVB]ZEJLSNY\^J[CUVSA_QLFC^RQHUPH[P[NRWCCMLSNPOD_ESALHUK@TDFUZHBLJ\XGKL^NXA\EVHSP[D_C^B_^JCX^W]CHBAX]POG@SSAZQ\LE[DCNMUPG_VSC@VJM X-Spam-Status: No, hits=-10.8 required=5.0 tests=EMAIL_ATTRIBUTION,NOSPAM_INC,QUOTED_EMAIL_TEXT,REFERENCES, SPAM_PHRASE_02_03,USER_AGENT,USER_AGENT_MOZILLA_UA, X_ACCEPT_LANG version=2.41 Xref: archiver1.google.com comp.std.c++:16444 ===================================== MODERATOR'S COMMENT: Please try not to quote moderation footers when posting. ===================================== END OF MODERATOR'S COMMENT I once wrote a paper titled "Type Integer Considered Harmful". But it was too radical. I addressed this issue by viewing numeric types as ranges, and insisting that the compiler choose intermediate types in expressions such that overflow in a compiler-sized temporary was impossible unless an overflow in the programmer-sized result was inevitable. This usually doesn't result in multiple-precision arithmetic, and when it does, you needed it. The "size of the machine" would then no longer be visible to the programmer. Too radical, and, once the ones-complement and the 36-bit machines died off, unnecesssary. John Nagle Animats Philippe Mori wrote: > In this case (I'm not sure what would be the rule if longs are 64 bit), both > values would be converted to unsigned before the comparison and -1 will > become a really big number and the comparison won't give the expected > result... > > In pratice this is often the case when comparing signed and unsigned value, > we do not get the expected result. > > For constants, I think that they are signed except when they do not fit the > range of signed value. The constant would be considered unsigned... > > I do not think this could be easily changed. The best thing to do is to > properly select the appropraite type for your constants and variables > (either all signed or all unsigned). In some case, unsigned value could be > converted to signed value explicitly because we knows that it is not > probable to have a value bigger than the range of an unsigned. Better yet, > validate it before doing the conversion. > > --- > [ 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.jamesd.demon.co.uk/csc/faq.html ] > > --- [ 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.jamesd.demon.co.uk/csc/faq.html ]