From -4137202538488541094 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,ede379f5dbbc1549 X-Google-Attributes: gidf78e5,public From: fjh@cs.mu.OZ.AU (Fergus Henderson) Subject: Re: Suggestion: "typeof" keyword Date: 1999/08/29 Message-ID: <7q90mb$pqr$1@mulga.cs.mu.OZ.AU>#1/1 X-Deja-AN: 518351514 X-Nntp-Posting-Host: mundook.cs.mu.oz.au Approved: stephen.clamage@sun.com (comp.std.c++) References: <7nt3vl$1oe$1@nnrp1.deja.com> <7oh7o8$t3f$1@nnrp1.deja.com> <7ol6hi$ej9$2@news.BelWue.DE> <7oup0a$8g2$1@nnrp1.deja.com> <37B3C2AD.5AB722AE@lucent.com> <37B5A571.449B@wanadoo.fr> <37B908A8.717CAC2C@lucent.com> <7pcvjs$tk4$1@nnrp1.deja.com> <7phk8n$b26$1@nnrp1.deja.com> <37BD2185.C0047293@physik.tu-muenchen.de> <7pk6r6$689$1@nnrp1.deja.com> <37C3F3C5.CAA574E8@physik.tu-muenchen.de> Organization: Computer Science, The University of Melbourne X-UID: 0000000001 X-Status: $$$T Newsgroups: comp.std.c++ Originator: clamage@taumet Christopher Eltschka writes: >niklasb@my-deja.com wrote: >> >> You've convinced me. The reference should be stripped, >> but the CV qualifier should be retained. Just to give >> something concrete to talk about, let me try once again >> to suggest a set of rules: ... >> 3 Within the context of a typeof expression, a temporary >> object of any type T can be instantiated using >> >> - initialization notation, T(), whether or not >> T has a default constructor, or >> >> - cast notation, (T)expr, whether or not a >> conversion from typeof(expr) to T exists. Why allow both of these? Surely allowing one of them would be sufficient. I still don't see why any of these is better than `*(T*)NULL'. >I'd restrict this to special expressions; a good candidate >would be the same as currently the null pointer constant, >since this already is very special. > >Thus in typeof expressions > > (T)0 would be legal and an rvalue > (T&)0 would be legal and an lvalue You could use `(T)*(T*)NULL' for a null pointer, although admittedly that is not particularly pleasant syntax. I think the need to distinguish between rvalues and lvalues would be rare. If you don't like that syntax, you can easily define template functions template T rvalue(); template T& lvalue(); and then use `rvalue()' and `lvaue()'. -- Fergus Henderson | "I have always known that the pursuit WWW: | of excellence is a lethal habit" PGP: finger fjh@128.250.37.3 | -- the last words of T. S. Garp. [ 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 ]