From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,FREEMAIL_FROM autolearn=ham autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 103376,56131a5c3acc678e X-Google-Attributes: gid103376,public X-Google-ArrivalTime: 2003-12-07 19:36:18 PST Path: archiver1.google.com!news2.google.com!newsfeed2.dallas1.level3.net!news.level3.com!crtntx1-snh1.gtei.net!news.gtei.net!newsfeed1.easynews.com!easynews.com!easynews!cyclone1.gnilink.net!spamkiller2.gnilink.net!nwrdny01.gnilink.net.POSTED!53ab2750!not-for-mail From: Hyman Rosen User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.5) Gecko/20031008 Thunderbird/0.3 X-Accept-Language: en-us, en MIME-Version: 1.0 Newsgroups: comp.lang.ada Subject: Re: Question about OO programming in Ada References: <5JmdnUF_9o_ABE-iRTvUrg@rapidnet.com> <1273941.m4G3ZzughP@linux1.krischik.com> In-Reply-To: Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Message-ID: Date: Mon, 08 Dec 2003 03:36:16 GMT NNTP-Posting-Host: 162.84.211.17 X-Complaints-To: abuse@verizon.net X-Trace: nwrdny01.gnilink.net 1070854576 162.84.211.17 (Sun, 07 Dec 2003 22:36:16 EST) NNTP-Posting-Date: Sun, 07 Dec 2003 22:36:16 EST Xref: archiver1.google.com comp.lang.ada:3212 Date: 2003-12-08T03:36:16+00:00 List-Id: James Rogers wrote: > I understood "virtual" is a modifier for C++ functions. A C++ class > with non-virtual functions can still be extended with new data members, > or even with new virtual function members. Please correct me if I am > wrong. A C++ class with no virtual functions (of its own or inherited) is the equivalent of an untagged Ada type. A class with any virtual function is the equivalent of a tagged type. The typical C++ implementation of virtual functions (and I imagine the Ada one as well) is to include in the class a pointer to a dispatch table. While a C++ class has no virtual functions, the compiler does not place such a dispatch pointer in the class. When a virtual function is added, the compiler adds the dispatch pointer.