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: 103376,73057f1a3ca11607 X-Google-Attributes: gid103376,public X-Google-Language: ENGLISH,ASCII Path: g2news1.google.com!news2.google.com!proxad.net!news.tele.dk!news.tele.dk!small.news.tele.dk!newspeer2.se.telia.net!se.telia.net!masternews.telia.net.!newsb.telia.net.POSTED!not-for-mail From: =?ISO-8859-1?Q?Bj=F6rn_Persson?= User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.4.1) Gecko/20031114 X-Accept-Language: sv, sv-se, sv-fi, en-gb, en-us, en MIME-Version: 1.0 Newsgroups: comp.lang.ada Subject: Re: Is T an ancestor of T? References: In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: quoted-printable Message-ID: Date: Wed, 20 Oct 2004 23:33:33 GMT NNTP-Posting-Host: 217.209.116.179 X-Complaints-To: abuse@telia.com X-Trace: newsb.telia.net 1098315213 217.209.116.179 (Thu, 21 Oct 2004 01:33:33 CEST) NNTP-Posting-Date: Thu, 21 Oct 2004 01:33:33 CEST Organization: Telia Internet Xref: g2news1.google.com comp.lang.ada:5550 Date: 2004-10-20T23:33:33+00:00 List-Id: Georg Bauhaus wrote: > So we know there is exactly one ultimate ancestor for each type T. > If T is at the root of a derivation hierarchy of height 0, > is there a named type that is the ultimate ancestor of T? > Is it T? By 10.d I would say yes. Yes. > By the last sentence of (10), > the ultimate ancestor (T) "is not a descendant of any other type". > So if T is the ultimate ancestor, it is not a descendant of T. > Which it is by the first sentence of (10). > I must be missing something. Specific types? Maybe it's the word "other" you're missing? If it read "not a descendant = of any type", then there would be a contradiction as you say, but it=20 reads "not a descendant of any *other* type". "Other" must mean "other=20 than itself". > Then if D is new T with ..., is T the ultimate ancestor of D? > (Again I would agree that it is.) Yes. > If T is the ultimate ancestor of T (and T is the ultimate > ancestor of D if D had been defined), can GNAT be right when > (T with n =3D> 0) is accepted as an extension aggregate of specific > type T? I still don't think so. Me neither. By the way, did you notice that class-wide types aren't ancestors or=20 descendants of themselves? --=20 Bj=F6rn Persson PGP key A88682FD omb jor ers @sv ge. r o.b n.p son eri nu