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: border1.nntp.dca3.giganews.com!border3.nntp.dca.giganews.com!border1.nntp.dca.giganews.com!nntp.giganews.com!goblin3!goblin.stu.neva.ru!news-1.dfn.de!news.dfn.de!news.uni-weimar.de!medsec1.medien.uni-weimar.de!lucks From: Stefan.Lucks@uni-weimar.de Newsgroups: comp.lang.ada Subject: Re: Is this expected behavior or not Date: Fri, 5 Apr 2013 21:02:43 +0200 Organization: Bauhaus-Universitaet Weimar Message-ID: References: <1gnmajx2fdjju.1bo28xwmzt1nr.dlg@40tude.net> <3gv2jwc95otm.pl2aahsh9ox8.dlg@40tude.net> <1gkxiwepaxvtt$.u3ly33rbwthf.dlg@40tude.net> <1fmcdkj58brky.bjedt0pr39cd$.dlg@40tude.net> <1bj564vat3q1j$.1s4d00rlzx4ux$.dlg@40tude.net> <1cfhriq4xpg9s$.3yl33z705wpn$.dlg@40tude.net> <16wai67izvmu5.13yz864sx1cqd$.dlg@40tude.net> NNTP-Posting-Host: medsec1.medien.uni-weimar.de Mime-Version: 1.0 Content-Type: MULTIPART/MIXED; BOUNDARY="8323329-1128574358-1365188564=:31746" X-Trace: tigger.scc.uni-weimar.de 1365188634 21984 141.54.178.228 (5 Apr 2013 19:03:54 GMT) X-Complaints-To: news@tigger.scc.uni-weimar.de NNTP-Posting-Date: Fri, 5 Apr 2013 19:03:54 +0000 (UTC) X-X-Sender: lucks@debian In-Reply-To: <16wai67izvmu5.13yz864sx1cqd$.dlg@40tude.net> User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) X-Original-Bytes: 4452 Xref: number.nntp.dca.giganews.com comp.lang.ada:180938 Date: 2013-04-05T21:02:43+02:00 List-Id: This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. --8323329-1128574358-1365188564=:31746 Content-Type: TEXT/PLAIN; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE On Fri, 5 Apr 2013, Dmitry A. Kazakov wrote: > On Fri, 5 Apr 2013 16:44:53 +0200, Stefan.Lucks@uni-weimar.de wrote: >> But the same is true for N and Z: every in Z has an additive inverse, bu= t >> not every number in N. If the non-existence of a multiplicative inverse >> would justify different root types for Z and R, why should the >> non-existence of an additive inverse not justify different root types fo= r >> N and Z (Universal_Positive versus Universal_Integer). > > That depends solely on the application domain. Ada is a general-purpose language. We are discussing Ada's type concept=20 and not any specific application, so there is not "the application domain"= =20 anything could possibly depend on. >> As it turns out, the fact that Naturals and Positives have the same >> representation as Integers, while Float has a different one, matters mor= e >> than any "mathematical structure" ... > > Nope, representation never matter. Employee ID and task ID may have same > representation. That does not mean anything. Nominal type equivalence was= a > corner stone of Ada design. Dmitry, I admire your ability to make some correct claim, being out of=20 topic, and then pretending that this claim makes your point! ;-) Sure, one of the main strengths of Ada from its beginning is allowing the= =20 programmer to define different and intentionally incompatible types with=20 identical representations. But you are actually proposing the opposite: Making different types with=20 different representations intentionally compatible by introducing some=20 universal super-type and then formally deriving the different types from=20 the super-type. Actually another corner stone of Ada has been the language designers'=20 reluctance to introduce implicit conversions between types with different= =20 representations. Sure, some cases where implicit conversions take place=20 exist, but only very few. One example is the conversion of constants of=20 type Universal_Something into the right type. ------ I love the taste of Cryptanalysis in the morning! ------ --Stefan.Lucks (at) uni-weimar.de, Bauhaus-Universit=E4t Weimar, Germany-- --8323329-1128574358-1365188564=:31746--