From 6015358979707763815 X-Google-Thread: f78e5,eb811809d4f61b12 X-Google-Attributes: gidf78e5,public X-Google-Language: ENGLISH,ASCII Path: g2news2.google.com!news2.google.com!news.germany.com!newsfeed01.sul.t-online.de!t-online.de!newsfeed.vmunix.org!peer-uk.news.demon.net!kibo.news.demon.net!news.demon.co.uk!demon!stump.algebra.com!devnull From: kanze.james@neuf.fr (James Kanze) Newsgroups: comp.std.c++ Subject: Re: Using extended precision in floating point Date: Sun, 21 May 2006 07:33:50 GMT Organization: Aioe.org NNTP Server Lines: 44 Sender: mail2news@demon.net Approved: fjh@cs.mu.oz.au (Fergus Henderson , moderator of comp.std.c++) Message-ID: References: <1147882581.972497.100340@u72g2000cwu.googlegroups.com> <1148033537.225653.254200@j55g2000cwa.googlegroups.com> <1148043502.821551.249470@y43g2000cwc.googlegroups.com> NNTP-Posting-Host: news.news.demon.net Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: quoted-printable X-Trace: news.demon.co.uk 1148196856 25535 158.152.254.254 (21 May 2006 07:34:16 GMT) X-Complaints-To: abuse@demon.net NNTP-Posting-Date: Sun, 21 May 2006 07:34:16 +0000 (UTC) X-Original-To: std-c++@mailman.ucar.edu X-Robomod: STUMP, ichudov@algebra.com (Igor Chudov) X-User-Agent: Thunderbird 1.5.0.2 (X11/20060420) X-MIME-Autoconverted: from 8bit to quoted-printable by mulga.cs.mu.OZ.AU id k4L7Y2tF020144 X-Greylisting: NO DELAY (Relay+Sender autoqualified); processed by UCSD_GL-v2.1 on mailbox7.ucsd.edu; Sat, 20 May 2006 11:27:12 -0700 (PDT) X-Virus-Scanned: amavisd-new at cs.mu.OZ.AU X-Path: comp-std-cpp-robomod!not-for-mail X-Received: (from fjh@localhost) by mulga.cs.mu.OZ.AU (8.12.10+Sun/8.12.9/Submit) id k4L7Xo1l020078; Sun, 21 May 2006 17:33:50 +1000 (EST) X-Delivered-To: std-c++@ucar.edu X-Spamscanner: mailbox7.ucsd.edu (v1.6 Aug 4 2005 15:27:38, -2.8/5.0 3.0.4) X-Authentication-Warning: mulga.cs.mu.OZ.AU: fjh set sender to devnull@stump.algebra.com using -f X-Newsgroups: comp.std.c++ X-MailScanner: PASSED (v1.2.8 93992 k4KIR91d099223 mailbox7.ucsd.edu) Xref: g2news2.google.com comp.std.c++:2073 wade@stoner.com wrote: > kanze wrote: >> From what I understand, adding the [g++] option -ffloat-store >> should cause conformant behavior. >> ... I think that the intent [of the standard] is that even >> when extended precision is used in sub-expressions, the >> programmer can force normal precision by means of a cast or >> an assignment. The standard can certainly be interpreted >> this way, but I'm not sure that other interpretations are not >> possible. > I think that the documented behavior of -ffloat-store matches > this "intent." However, the g++ emails suggest that on x86, > -ffloat-store applies to named variables, but not to > temporaries. This would suggest that a cast may not force > normal precision (unless the result of the cast is directly > used in an assignment). The intent is for it only to apply to temporaries that result from a cast. I suspect that this is not necessarily trivial in the compiler -- if an expression is of type double, and I cast it to double, it's quite possible that there is no way of expressing this in the intermediate language that is passed to the back end. > This is mostly a quibble. I'd expect most programmers would use > assignment-to-a-named-variable for this operation. Well, I would:-). --=20 James Kanze kanze.james@neuf.fr Conseils en informatique orient=E9e objet/ Beratung in objektorientierter Datenverarbeitung 9 place S=E9mard, 78210 St.-Cyr-l'=C9cole, 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-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.comeaucomputing.com/csc/faq.html ]