From -1977844894215363527 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: 1999/08/13 Message-ID: <7p0lub$2i3$1@mulga.cs.mu.OZ.AU>#1/1 X-Deja-AN: 512289900 X-Nntp-Posting-Host: murlibobo.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> <37B2DA79.3A02@wanadoo.fr> Organization: Computer Science, The University of Melbourne X-UID: 0000000001 X-Status: $$$T Newsgroups: comp.std.c++ Originator: clamage@taumet Valentin Bonnard writes: >Hyman Rosen wrote: > >> If you think about it, there is a fundamental asymmetry in function >> template argument deduction, in that the deduced types are fully >> available to be used within the function, > >This ``asymmetry'' is called scoping, by the way. > >I am not sure that scoping has to be ``corrected''. `declare' and even `typeof' would both preserve scoping. I think it's more an issue of orthogonality rather than asymmetry. Type deduction and function calls are separate things. C++ compilers know how to do type deduction, and knows how to do function calls. But for various reasons, mostly historical IMHO, C++ doesn't provide any way to do type deduction without doing a function call. `typeof' could remedy that. However, `typeof' is not quite as general as argument type deduction. For example, you may know that a particular variable has type `foo', and you may want to find out what `T' is; you can do that with argument type deduction, but you can't do it with `typeof'. Still, `typeof' is a simple extension in the following senses: - it's easy to implement (C++ compilers already have the necessary infrastructure for doing type deduction, so I think it should basically be just a matter of adding the front-end syntax) - it's easy to specify - it's easy for programmers to understand I'm not sure how useful it is, but as far as extensions go, the cost of adding this one is very low. -- 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 ]