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=unavailable autolearn_force=no version=3.4.4 Path: eternal-september.org!reader01.eternal-september.org!reader02.eternal-september.org!feeder.eternal-september.org!aioe.org!.POSTED!not-for-mail From: "Dmitry A. Kazakov" Newsgroups: comp.lang.ada Subject: Re: about inheritance of subtypes and entities (such as constants) related to a type in the same package Date: Thu, 31 May 2018 21:59:46 +0200 Organization: Aioe.org NNTP Server Message-ID: References: <534965d3-e494-476b-8a91-6cf9f376c020@googlegroups.com> NNTP-Posting-Host: CvkHMVp693S8Z+lk11jyqg.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; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 X-Notice: Filtered by postfilter v. 0.8.3 Content-Language: en-US Xref: reader02.eternal-september.org comp.lang.ada:52819 Date: 2018-05-31T21:59:46+02:00 List-Id: On 2018-05-31 20:53, Dan'l Miller wrote: > On Thursday, May 31, 2018 at 12:37:07 PM UTC-5, Dmitry A. Kazakov wrote: >> On 2018-05-31 04:29 PM, Dan'l Miller wrote: >>> Conversely, subtyping in Ada does none of that type-extension stuff: no >>>  additional data/cardinality-of-the-members-of-the-set, no additional >>  > routines/behavior, no arbitrary refinement of behavior of overridden/copied >>>  routines/operations. Instead, subtyping in Ada is strictly subjecting the >>>  parent type to an additional membership-narrowing predicate, such as subset >>  > in set theory. Randy likewise spoke of membership on other branches of this >>  > thread. >> >> Untrue. Ada 83 subtyping extends the supertype (base type), because it >> exports operations defined on the subtype to the base type. Ada 83 >> subtyping introduces an equivalent type, which is both sub- and >> supertype of the base. > > If Ada83 untagged subtyping is type extension, please provide even a single characteristic that was extended/added/supplemented instead of contracted/subtracted/elided by the predicate. Elementary: subtype Extension is Integer; procedure Extended_Operation (X : Extension) is null; X : Integer; Y : Extension; begin Extended_Operation (X); -- See #1 Extended_Operation (Y); -- See #2 The subtype Extension extends Integer with Extended_Operation, which has two separate meanings: 1. The base type Integer has now a new operation: new Integer interface = old Integer interface + Extended_Operation 2. The subtype Extension extends inherited Integer's set of operations: Extended interface = old Integer interface + Extended_Operation -- Regards, Dmitry A. Kazakov http://www.dmitry-kazakov.de