From -6330919865501899056 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,bb2cedb5166b3859 X-Google-Attributes: gidf78e5,public X-Google-ArrivalTime: 2001-11-12 03:21:02 PST Path: archiver1.google.com!news1.google.com!newsfeed.stanford.edu!news-spur1.maxwell.syr.edu!news.maxwell.syr.edu!dispose.news.demon.net!news.demon.co.uk!demon!mail2news.demon.co.uk!not-for-mail From: "Anthony Williams" Newsgroups: comp.std.c++ Subject: Re: Typeof considered harmful (long) Date: Mon, 12 Nov 2001 11:20:28 GMT Approved: Fergus Henderson , moderator of comp.std.c++ Message-ID: <9so3n6$14m2on$1@ID-49767.news.dfncis.de> References: X-Trace: mail2news.demon.co.uk 1005564034 mail2news:29692 mail2news mail2news.demon.co.uk X-Complaints-To: abuse@demon.net X-Mail2News-Path: news.demon.net!mulga.cs.mu.oz.au X-Authentication-Warning: mulga.cs.mu.OZ.AU: fjh set sender to devnull@stump.algebra.com using -f X-Robomod: STUMP, ichudov@algebra.com (Igor Chudov) X-Orig-NNTP-Posting-Host: h96s2a160n47.user.nortelnetworks.com (47.160.2.96) X-Orig-X-Trace: fu-berlin.de 1005556263 38472471 47.160.2.96 (16 [49767]) X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 5.50.4807.1700 X-MimeOLE: Produced By Microsoft MimeOLE V5.50.4807.1700 Lines: 48 Xref: archiver1.google.com comp.std.c++:8131 "Brian Parker" wrote in message news:fTlH7.2855$c87.79835@ozemail.com.au... [snip] > template > R func(P1 p1, P2 p2) > { > L local = p1 * p2; > > return local * p2; > } [snip] > Proposed solution by extending C++ type deduction: > The fundamental problem is that L and R in the above template function are > essentially non-deduced contexts. A solution, then is to specify that after > function argument deduction, if function template parameters remain > non-deduced and are not used as part of the function signature (excluding > the return type), then the type is deduced to be that of the initializing > expression (or more accurately, it is deduced by the same algorithm that a > function parameter is deduced to match an initialising function argument). > > So, for example, L above will be deduced to be the type of the initializing > expression "p1 * p2", and R will be deduced as the type of the return > expression "local * p2". This would break existing template code, which allows L and R to be non-deduced, and explicitly specified. This is a feature used in real code. I agree that typeof() can be clumsy, but this is not a viable alternative. Anthony -- Anthony Williams Software Engineer, Nortel Networks Optical Components Ltd The opinions expressed in this message are not necessarily those of my employer --- [ 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.research.att.com/~austern/csc/faq.html ]