From -2958015444595381691 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,bed6baff9e441d5c X-Google-Attributes: gidf78e5,public X-Google-ArrivalTime: 2003-02-05 16:52:07 PST Path: archiver1.google.com!news1.google.com!newsfeed.stanford.edu!bloom-beacon.mit.edu!news-peer.gip.net!news.gsl.net!gip.net!opentransit.net!newsfeed.icl.net!newsfeed.fjserv.net!kibo.news.demon.net!mutlu.news.demon.net!demon!mail2news.demon.co.uk!devnull From: dlagno@mail.nnov.ru (Denis Lagno) Newsgroups: comp.std.c++ Subject: Re: proposal: "virtual restrict" inheritance Date: Thu, 6 Feb 2003 00:52:05 +0000 (UTC) Organization: http://groups.google.com/ Lines: 111 Approved: fjh@cs.mu.oz.au (Fergus Henderson , moderator of comp.std.c++) Message-ID: <5a0f3464.0302031509.465980e3@posting.google.com> References: <5a0f3464.0302020455.25d887a9@posting.google.com> <5a0f3464.0302030047.64f63c34@posting.google.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit X-Trace: mail2news.demon.co.uk 1044492725 4156 10.0.0.1 (6 Feb 2003 00:52:05 GMT) X-Complaints-To: abuse@demon.net NNTP-Posting-Date: Thu, 6 Feb 2003 00:52:05 +0000 (UTC) X-Received: from mulga.cs.mu.oz.au ([128.250.1.22]) by news.demon.co.uk with esmtp (Exim 4.05) id 18gaGn-00014l-00 for mail2news@news.news.demon.net; Thu, 06 Feb 2003 00:52:03 +0000 X-Received: from localhost (localhost [[UNIX: localhost]]) by mulga.cs.mu.OZ.AU id LAA18695; Thu, 6 Feb 2003 11:51:57 +1100 (EST) X-Authentication-Warning: mulga.cs.mu.OZ.AU: fjh set sender to devnull@stump.algebra.com using -f X-Path: comp-std-cpp-robomod!not-for-mail X-Robomod: STUMP, ichudov@algebra.com (Igor Chudov) X-Delivered-To: std-c++@ncar.ucar.edu X-Newsgroups: comp.std.c++ X-NNTP-Posting-Date: 3 Feb 2003 23:09:45 GMT X-Spam-Status: No, hits=-5.5 required=5.0 tests=GAPPY_TEXT,NOSPAM_INC,REFERENCES,SPAM_PHRASE_01_02 version=2.41 Xref: archiver1.google.com comp.std.c++:17801 In more formal words. beginning of [class.derived] clause now states: ### 1 A list of base classes can be specified in a class definition using the notation: base-clause: : base-specifier-list base-specifier-list: base-specifier base-specifier-list , base-specifier base-specifier: ::opt nested-name-specifieropt class-name virtual access-specifieropt ::opt nested-name-specifieropt class-name access-specifier virtualopt ::opt nested-name-specifieropt class-name access-specifier: private protected public ### It should be changed to: ### 1 A list of base classes can be specified in a class definition using the notation: base-clause: : base-specifier-list base-specifier-list: base-specifier base-specifier-list , base-specifier base-specifier: ::opt nested-name-specifieropt class-name virtual ::opt nested-name-specifieropt class-name access-specifier ::opt nested-name-specifieropt class-name restrict ::opt nested-name-specifieropt class-name virtual access-specifier restrictopt ::opt nested-name-specifieropt class-name virtual restrict access-specifieropt ::opt nested-name-specifieropt class-name access-specifier virtual restrictopt ::opt nested-name-specifieropt class-name access-specifier restrict virtualopt ::opt nested-name-specifieropt class-name restrict access-specifier virtualopt ::opt nested-name-specifieropt class-name restrict virtual access-specifieropt ::opt nested-name-specifieropt class-name access-specifier: private protected public ### As well we should add subclause [class.restrict]. (in following text w.r.t. = with respect to) ### 10.x Restricted inheritance [class.restrict] 1 A base class specifier that contains the keyword restrict, specifies a restricted base class. We say that a class without base classes is not restricted w.r.t. any class. A class with direct restricted base class R is restricted via R w.r.t. R and all base classes of R. A class with direct base class B is restricted via B w.r.t. all classes which B is restricted w.r.t. A class X is restricted w.r.t. to class A if class X is restricted via some class w.r.t class A. 2 A program in which some fixed class X is restricted via more than one class w.r.t. some fixed class B, is ill-formed. [Example: class A1 { /* ... /* }; class A2 { /* ... /* }; class B1: A1 { /* ... /* }; class B2: A2 { /* ... /* }; class C: A1, A2 { /* ... /* }; class D1: B1, C { /* ... /* }; class D2: restrict B2, C { /* ... /* }; class E1: restrict D1 { /* ... /* }; class E2: D2 { /* ... /* }; class F: E1, E2 { /* ... /* }; Here F is restricted via E1 w.r.t. D1, B1, C, A1 and A2. F also is restricted via E2 w.r.t. B2 and A2. Hence this program is ill-formed. --end example] ### OK, what problems does it solve?? (1) it enables optimisation of virtual inheritance that cannot be done if compiler sees only 1 translation unit. (2) problem raised by Daniel Gutson -- how implement exclusive inheritance. --- [ 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.jamesd.demon.co.uk/csc/faq.html ]