From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.5-pre1 (2020-06-20) on ip-172-31-74-118.ec2.internal X-Spam-Level: X-Spam-Status: No, score=-1.9 required=3.0 tests=BAYES_00 autolearn=ham autolearn_force=no version=3.4.5-pre1 Path: eternal-september.org!reader02.eternal-september.org!aioe.org!5WHqCw2XxjHb2npjM9GYbw.user.gioia.aioe.org.POSTED!not-for-mail From: "Dmitry A. Kazakov" Newsgroups: comp.lang.ada Subject: Re: Simple example on interfaces Date: Tue, 26 Jan 2021 11:25:37 +0100 Organization: Aioe.org NNTP Server Message-ID: References: <9e1b5d67-be08-4f53-aadc-fbed761a8c24n@googlegroups.com> NNTP-Posting-Host: 5WHqCw2XxjHb2npjM9GYbw.user.gioia.aioe.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit X-Complaints-To: abuse@aioe.org User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.1 X-Notice: Filtered by postfilter v. 0.9.2 Content-Language: en-US Xref: reader02.eternal-september.org comp.lang.ada:61208 List-Id: On 2021-01-26 10:37, J-P. Rosen wrote: > Le 25/01/2021 à 23:06, Dmitry A. Kazakov a écrit : >> Ada interface is a type that has interface and no implementation. [It >> is a silly idea inherited from Java.] >> > To make it look a little less silly, think of it as a promise: a type > that implements an interface promises to provide a certain number of > operations. I agree. I meant that Ada 95 had that already: type Interface is abstract tagged null record; There was no need to introduce it as a separate concept. I think the real reason was laziness. Vendors did not want to implement full multiple inheritance. Adding a simple constraint on the base types looked bad and also breached privacy: type Is_It_Interface is abstract tagged private; private type Is_It_Interface is abstract tagged null record; > Then you can define algorithms that work on any type that fulfills the > promises. > > To me, the big benefit of interfaces is that it is NOT inheritance; you > say that your type provides some operations, without needing to classify > it with an is-a relationship. But you do. When you say that T provides F that in other words means T *is-a* member of a class that provides F. Interface is merely a formalization of that. > (I can hear screamings of pure-OO people who will not agree with me ;-) ) OO muddied a lot of water. To me things are quite pragmatic. How do I spell in the language the fact that Long_Integer is an integer? If Integer is an integer and Long_Integer is an integer can I write a program that works on integers? Can it be the *same* program for each instance of? Simple, natural questions. -- Regards, Dmitry A. Kazakov http://www.dmitry-kazakov.de