From 4944305901141055313 X-Google-Thread: f78e5,c9a289c55d59e43d X-Google-Attributes: gidf78e5,public X-Google-Language: ENGLISH,ASCII Path: g2news2.google.com!news1.google.com!border1.nntp.dca.giganews.com!border2.nntp.dca.giganews.com!nntp.giganews.com!local01.nntp.dca.giganews.com!nntp.speakeasy.net!news.speakeasy.net.POSTED!not-for-mail NNTP-Posting-Date: Tue, 18 Jul 2006 08:20:01 -0500 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 From: "kanze" Newsgroups: comp.std.c++ Subject: Re: non-type template parameter in the new std. Organization: http://groups.google.com Message-ID: <1153227619.814308.53700@m73g2000cwd.googlegroups.com> References: <1152726032.559269.324790@75g2000cwc.googlegroups.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" X-Complaints-To: groups-abuse@google.com User-Agent: G2/0.2 X-HTTP-UserAgent: Mozilla/5.0 (X11; U; SunOS sun4u; en-US; rv:1.0.1) Gecko/20020920 Netscape/7.0,gzip(gfe),gzip(gfe) Complaints-To: groups-abuse@google.com Injection-Info: m73g2000cwd.googlegroups.com; posting-host=62.160.54.162; posting-account=qsfl8gwAAABZGaLp2a7FeTfDkJamzWYW X-Virus-Scanned: amavisd-new at ucar.edu X-Virus-Scanned: amavisd-new at csse.unimelb.edu.au Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by mulga.csse.unimelb.edu.au id k6ID13PH006813 Approved: Fergus Henderson , moderator of comp.std.c++ X-Virus-Scanned: amavisd-new at csse.unimelb.edu.au Date: Tue, 18 Jul 2006 08:18:36 CST Lines: 89 NNTP-Posting-Host: 65.182.171.162 X-Trace: sv3-NANtF741akrJ0H4tcoAuk/qyjz57btzkPbkfBa78v/QeplEli1pELKtJqKSK8iOKf5nNHbn6GulM/p1!IgX+vNM47Rdy1pBNkZnMa0v6HmqAtpiY4GBH75xbM+UKWZiQ4CZcfuea7zCEGLYjSmzZe9tatr5/!jKtJtlahm7rv9TgrCjmuA6+hVhzV1GFoYno54tSu5Q== X-Complaints-To: abuse@speakeasy.net X-DMCA-Complaints-To: abuse@speakeasy.net X-Abuse-and-DMCA-Info: Please be sure to forward a copy of ALL headers X-Abuse-and-DMCA-Info: Otherwise we will be unable to process your complaint properly X-Postfilter: 1.3.32 Xref: g2news2.google.com comp.std.c++:2819 Dave Harris wrote: > richard@ex-parrot.com (Richard Smith) wrote (abridged): > > werasm wrote: > > > 1) Are floating point numbers non-type template parameters in the > > > latest standard. > > Not at present. The rationale being that when cross > > compiling, the compiler would need to exactly emulate the > > floating point behaviour of the target processor, right down > > to the details of rounding, handling of NaNs and infinites, > > etc. > Actually, as I understand it the problem is one of type > checking. It's definitely one of type checking. > Given: > template struct X {}; > void func( X<0.3333> ) {} > void func( X<1.0/3.0> ) {} > is this two definitions of the same function that violates the > one-definition rule, or are there two functions that take > arguments of different types? How is this different from: template< int v > struct X {} ; void func( X< 0 > ) {} void func( X< -1 & 1 > ) {} // Consider a 1's complement machine or for that matter, even: template< typename T > struct X{} ; void func( x< unsigned int > ) {} void func( X< size_t > ) {} > The answer depends on the precision of the floating > point, And with signed integers, and with type arguments in the presence of typedef's. > so we can't say whether the program is type-correct without > knowing more about the implementation than we should. > This is not really about cross-compiling. It is about *all* > compilers being consistent, rather than one compiler emulating > one other processor. I don't think it's that black and white. The issue of cross compilation means that a compiler must fully emulate the floating point hardware of the target platform if it is to be consistent for that platform. This is already true for int, of course, but emulating 1's complement (if necessary) is a lot easier than emulating floating point (and is already necessary anyway---something like "#if (-1 & 1) == 0" is probably in actual use somewhere to determine whether the target is 1's complement or not). Where as with floating point, on the other hand... It may not be just cross compilation. On some machines 1.0/3.0 is equal to 0.33333333333333333 if the value is assigned to memory, but not if the compiler manages to keep all of the intermediate results in a register. Globally, it's a thorny issue, and I think that there are a variety of motivations behind not supporting it: some due to cross compilation, others not. (One possibility: allow it, but don't allow anything but floating point literals as arguments, and define equality as absolute equality over the real numbers.) -- James Kanze GABI Software 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-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.comeaucomputing.com/csc/faq.html ]