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 autolearn=ham autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 103376,1116ece181be1aea X-Google-Attributes: gid103376,public X-Google-ArrivalTime: 2003-09-15 07:00:22 PST Path: archiver1.google.com!news1.google.com!newsfeed.stanford.edu!headwall.stanford.edu!fu-berlin.de!uni-berlin.de!tar-alcarin.cbb-automation.DE!not-for-mail From: Dmitry A. Kazakov Newsgroups: comp.lang.ada Subject: Re: Can MI be supported? (Was: Is the Writing on the Wall for Ada?) Date: Mon, 15 Sep 2003 16:08:08 +0200 Message-ID: <76hbmvg0fvuii8u4dm0jjq2pp2cjh5ppur@4ax.com> References: <3F5F7FDC.30500@attbi.com> <3F636281.7010509@attbi.com> NNTP-Posting-Host: tar-alcarin.cbb-automation.de (212.79.194.111) Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Trace: news.uni-berlin.de 1063634420 26312119 212.79.194.111 (16 [77047]) X-Newsreader: Forte Agent 1.8/32.548 Xref: archiver1.google.com comp.lang.ada:42524 Date: 2003-09-15T16:08:08+02:00 List-Id: On Sun, 14 Sep 2003 19:33:02 -0400, "Warren W. Gay VE3WWG" wrote: >"Robert I. Eachus" wrote in message news:3F636281.7010509@attbi.com... >> Warren W. Gay VE3WWG wrote: >> In Ada we have gone the extra mile so that you can do view conversions >> on objects to an ancestor type. So even when you derive from a tagged >> type and add state, you can still do a view conversion and look at an >> object of the child type as if it isa member of the parent's class. > >Right, but where is the conflict in MI in this? If I "convert" >C to B, then why not let me look at the "B" view using MI? >If I convert C to A, then why not allow me the use of the "A" view? It is a question of definition. If to view "C" as "B" we need a conversion, then it is probably rather an interface inheritance than classical implementation inheritance. >From my point of view, which most people are disagree with (:-)), there is absolutely no difference, how "view" conversion is achieved, whether by shifting a reference or by creation a new object. From the interface point of view, only the fact that this can achived counts. The rest is just implementation details. >OK, so MI can mess up the "is a" test if I understand correctly >(it leads to "incompatible logical conclusions"). No, it is "IS-A" which leads to incompatible logical conclusions! (:-)) Especially when "substitutable-for" and "interchangeable-with" are mixed. --- Regards, Dmitry Kazakov www.dmitry-kazakov.de