From 8765630846685196353 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,2bb87329d23dffd0 X-Google-Attributes: gidf78e5,public From: Martin von Loewis Subject: Re: why ::template in qualified id? Date: 2000/05/13 Message-ID: #1/1 X-Deja-AN: 622683443 Approved: Fergus Henderson , moderator of comp.std.c++ References: <3914163C.199321C8@earthlink.net> X-Authentication-Warning: mulga.cs.mu.OZ.AU: fjh set sender to devnull@stump.algebra.com using -f X-Complaints-To: abuse@demon.net X-Mail2News-Path: news.demon.net!mulga.cs.mu.oz.au X-Trace: mail2news.demon.co.uk 958161315 mail2news:27311 mail2news mail2news.demon.co.uk Organization: Humboldt University Berlin, Department of Computer Science X-Robomod: STUMP, ichudov@algebra.com (Igor Chudov) NNTP-Posting-Date: 12 May 2000 19:47:24 GMT Newsgroups: comp.std.c++ Larry Evans writes: > The ISO/IEC 14882 standard in 5.1 para 7 shows qualified-id may have > ::template substring; however, para 7 doesn't say when this is > useful. Could someone please explain this to me? It is needed on a lexical level to determine the meaning of "<". Normally, given X::foo::c you look up X, then X::foo. If it is a template, the '<' starts the template parameters, so this is an access to member c of X::foo. Otherwise, this is equivalent to (X::foo < a), (b > ::c). Now, if X is a template parameter, foo is a dependent name, and you can't tell whether X::foo is a template or not until instantiation time. Unfortunately, that means you could not parse that expression. So the rule is: If X is a template parameter, the '<' parses as an operator. If you mean it as a template argument list, you write X::template foo::c This is similar to the typename escape. Regards, Martin --- [ 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://reality.sgi.com/austern_mti/std-c++/faq.html ]