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=-0.3 required=5.0 tests=BAYES_00, REPLYTO_WITHOUT_TO_CC autolearn=no autolearn_force=no version=3.4.4 Path: eternal-september.org!reader01.eternal-september.org!reader02.eternal-september.org!news.eternal-september.org!news.eternal-september.org!news.eternal-september.org!feeder.eternal-september.org!feeder.erje.net!eu.feeder.erje.net!newsfeed.datemas.de!rt.uk.eu.org!aioe.org!.POSTED!not-for-mail From: "Dmitry A. Kazakov" Newsgroups: comp.lang.ada Subject: Re: Making sense of predicates Date: Tue, 22 Oct 2013 10:19:28 +0200 Organization: cbb software GmbH Message-ID: <9vlzla1igu9w$.1ifys2xkaugrn$.dlg@40tude.net> References: Reply-To: mailbox@dmitry-kazakov.de NNTP-Posting-Host: IenaDxMXK2hi7fvYcb+MlQ.user.speranza.aioe.org Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit X-Complaints-To: abuse@aioe.org User-Agent: 40tude_Dialog/2.0.15.1 X-Notice: Filtered by postfilter v. 0.8.2 Xref: news.eternal-september.org comp.lang.ada:17498 Date: 2013-10-22T10:19:28+02:00 List-Id: On Mon, 21 Oct 2013 23:35:59 -0500, Randy Brukardt wrote: > It should be one step (only). We'd need something like co-derivation for > that, which might make sense to pursue someday (the main reason would be to > get rid of access types altogether, but to do that you need some sort of > handle, like the container cursor -- and clearly you need to be able to > derive the container and its handle together). But that would be a big job > to define properly, it would take the existing inheritance rules and make > them much more complex. (There are already 3 pages of rules associated with > inheritance for derived types.) It is not only access types. It is relationships between types: Pointer - Target, Array - Index - Element, etc. If you try, as Ada designers keep on doing, to handle that at the language level for each built-in type individually, you indeed end up with something as horrific as accessibility rules are. That does not work. -- Regards, Dmitry A. Kazakov http://www.dmitry-kazakov.de