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!news.eternal-september.org!mx02.eternal-september.org!feeder.eternal-september.org!newsfeed.fsmpi.rwth-aachen.de!reality.xs3.de!news.jacob-sparre.dk!loke.jacob-sparre.dk!pnx.dk!.POSTED!not-for-mail From: "Randy Brukardt" Newsgroups: comp.lang.ada Subject: Re: Ichbiah's Letter Date: Mon, 27 Oct 2014 17:10:46 -0500 Organization: Jacob Sparre Andersen Research & Innovation Message-ID: References: <87mw8ivlr4.fsf@adaheads.sparre-andersen.dk> NNTP-Posting-Host: 24-196-82-226.static.mdsn.wi.charter.com X-Trace: loke.gir.dk 1414447848 27665 24.196.82.226 (27 Oct 2014 22:10:48 GMT) X-Complaints-To: news@jacob-sparre.dk NNTP-Posting-Date: Mon, 27 Oct 2014 22:10:48 +0000 (UTC) X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 6.00.2900.5931 X-RFC2646: Format=Flowed; Original X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.6157 Xref: news.eternal-september.org comp.lang.ada:22831 Date: 2014-10-27T17:10:46-05:00 List-Id: "Jacob Sparre Andersen" wrote in message news:87mw8ivlr4.fsf@adaheads.sparre-andersen.dk... >> https://duckduckgo.com/l/?kh=-1&uddg=http%3A%2F%2Fweb.elastic.org%2F~fche%2Fmirrors%2Fold-usenet%2Fada-with-null > > Reading the letter, I must say that I disagree with Ichbiah on some of > the Ada 9X features which he wanted dropped: > > + Aliased objects: > > I have more than one program I don't know how I could have implemented > sensibly without aliased objects. ... > - Accessibility (checks): > > It seems like this definitely is a part of the language, which has > ended up being too complicated for anyone to understand, but I am not > in a position to say anything sensible about how to avoid them in the > language. If you don't have aliased objects, then you don't need accessibility checks (because you can't get the access value of an object). So those two go together. Of course, getting the access value of a local object was one of the requirements for Ada 9x, so Ichbiah was essentially arguing to ignore one of the language requirements. The MRT had some leeway in doing that, but hardly enough to drop a number of major requirements. >+ Tagged types and dispatching: > > Well. Although Ichbiah puts tagged types on his list of complicated > features, he still argues for them further down in the letter. I > suppose that we agree. No, he argued for Simula classes; the fact that he lost that vote was the tripping point for his leaving the Ada 9x process and writing the letter in question. Why he thought that adding a new complex form of visibility was somehow better than extending an existing form of type (the Ada 83 derived type) still escapes me to this day. (At worst, they're about the same in overall complexity.) There may have been compelling arguments in favor of a class type, but "complexity" wasn't one of them. (Indeed, I recall arguing that basing anything on derived types, a very obscure corner of the language, was going to make things harder for Ada users. But the class type would not have helped that at all -- something totally new isn't easy to learn, either. And the actual problems in practice, particularly overriding, would have been just as messed up either way (the syntax has nothing to do with it).) Randy.