From 4203360328703358416 X-Google-Thread: f78e5,eb811809d4f61b12 X-Google-Attributes: gidf78e5,public X-Google-Language: ENGLISH,ASCII-7-bit Path: g2news2.google.com!news1.google.com!news3.google.com!border1.nntp.dca.giganews.com!nntp.giganews.com!newsfeed-east.nntpserver.com!nntpserver.com!statler.nntpserver.com!news.alt.net!comp-std-cpp-robomod!not-for-mail From: wade@stoner.com Newsgroups: comp.std.c++ Subject: Re: Using extended precision in floating point Date: Fri, 19 May 2006 12:58:11 CST Organization: http://groups.google.com Lines: 26 Approved: Fergus Henderson , moderator of comp.std.c++ Message-ID: <1148043502.821551.249470@y43g2000cwc.googlegroups.com> References: <1147882581.972497.100340@u72g2000cwu.googlegroups.com> <1148033537.225653.254200@j55g2000cwa.googlegroups.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" X-Trace: posting.google.com 1148043508 6015 127.0.0.1 (19 May 2006 12:58:28 GMT) X-Complaints-To: groups-abuse@google.com NNTP-Posting-Date: Fri, 19 May 2006 12:58:28 +0000 (UTC) Return-Path: X-Authentication-Warning: mulga.cs.mu.OZ.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 Delivered-To: std-c++@ucar.edu User-Agent: G2/0.2 X-HTTP-UserAgent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 1.1.4322; .NET CLR 2.0.50727; InfoPath.1),gzip(gfe),gzip(gfe) Complaints-To: groups-abuse@google.com Injection-Info: y43g2000cwc.googlegroups.com; posting-host=65.16.217.10; posting-account=1rcVOQwAAACiq302N7tDjZ9huexzBBxn X-Virus-Scanned: amavisd-new at ucar.edu X-Virus-Scanned: amavisd-new at cs.mu.OZ.AU X-Virus-Scanned: amavisd-new at cs.mu.OZ.AU Xref: g2news2.google.com comp.std.c++:2071 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). This is mostly a quibble. I'd expect most programmers would use assignment-to-a-named-variable for this operation. --- [ 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 ]