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-Thread: 103376,2ff5c149712ec0eb X-Google-Attributes: gid103376,public,usenet X-Google-Language: ENGLISH,ASCII-7-bit Newsgroups: comp.lang.ada Subject: Re: Ada Interfaces and the Liskov Substitution Principle References: <1179953657.839272.160320@a26g2000pre.googlegroups.com> <1179991769.376381.252010@m36g2000hse.googlegroups.com> <12h6mi42jcha0.7f9vfsnihjwr$.dlg@40tude.net> <1180003336.1163.29.camel@kartoffel> From: Markus E Leypold Organization: N/A Date: Fri, 25 May 2007 18:59:58 +0200 Message-ID: <83abvs7sa9.fsf@hod.lan.m-e-leypold.de> User-Agent: Some cool user agent (SCUG) Cancel-Lock: sha1:xr8Gcg0EkrYnhzD+8NLX2vSukh4= MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii NNTP-Posting-Host: 88.72.200.17 X-Trace: news.arcor-ip.de 1180111858 88.72.200.17 (25 May 2007 18:50:58 +0200) X-Complaints-To: abuse@arcor-ip.de Path: g2news1.google.com!news3.google.com!news.germany.com!storethat.news.telefonica.de!telefonica.de!news-fra1.dfn.de!newsfeed.arcor-ip.de!news.arcor-ip.de!not-for-mail Xref: g2news1.google.com comp.lang.ada:15943 Date: 2007-05-25T18:59:58+02:00 List-Id: > On Thu, 2007-05-24 at 10:02 +0200, Dmitry A. Kazakov wrote: > >> > Coming from C++, I have never seen any single example where assignment >> > made sense with polymorphic hierarchies. > ... >> >> > Do you know any such example? Can you show it? >> >> Marshaling objects. > > In fact, Eiffel has a relative, the assignment attempt > (written "?="). And the Eiffel arguments versus Liskov/Wing > are that the principles guiding program design should come > from the solution to a problem, not from models when these > cannot capture the solution. In a sense, it is argued that > that L/W substitution (and also co/contra-variance) violate > programming principles! Actually I'm a strong disbeliever in your approach. I doubt, that a solution that isn't mathematically beautiful and simple (i.e. fits a model) is viable in the long run. Intellectual friction will hampoer maintenance and optimization. Regards -- Markus