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 X-Google-Thread: a07f3367d7,16f1030bd366bf59 X-Google-Attributes: gida07f3367d7,public,usenet X-Google-NewGroupId: yes X-Google-Language: ENGLISH,ASCII Path: g2news1.google.com!news4.google.com!proxad.net!feeder1-2.proxad.net!newsfeed.straub-nv.de!uucp.gnuu.de!newsfeed.arcor.de!newsspool2.arcor-online.net!news.arcor.de.POSTED!not-for-mail From: "Dmitry A. Kazakov" Subject: Re: About the F-22 software bug Newsgroups: comp.lang.ada User-Agent: 40tude_Dialog/2.0.15.1 MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 8bit Reply-To: mailbox@dmitry-kazakov.de Organization: cbb software GmbH References: <4b6b15d2$0$929$ba4acef3@news.orange.fr> <4YKdnVFQX_suIPbWnZ2dnUVZ_rednZ2d@earthlink.com> <3050ef55-5dde-40ed-8a8f-a2daf245bf86@k19g2000yqc.googlegroups.com> Date: Fri, 5 Feb 2010 11:31:16 +0100 Message-ID: NNTP-Posting-Date: 05 Feb 2010 11:31:16 CET NNTP-Posting-Host: e7761fe9.newsspool3.arcor-online.net X-Trace: DXC=Oe09o;90jM;n`gW2MTm]<3McF=Q^Z^V384Fo<]lROoR18kFo`eP>L5[6LHn;2LCV>7enW;^6ZC`4IXm65S@:3>?b\;M5FKX2K1 X-Complaints-To: usenet-abuse@arcor.de Xref: g2news1.google.com comp.lang.ada:8905 Date: 2010-02-05T11:31:16+01:00 List-Id: On Fri, 5 Feb 2010 01:02:40 -0800 (PST), Martin wrote: > On Feb 5, 8:52�am, Ludovic Brenta wrote: >> Martin wrote on comp.lang.ada: >> >> >> >>> On Feb 5, 6:42�am, Dennis Lee Bieber wrote: >>> > On Thu, 04 Feb 2010 19:46:15 +0100, Pascal Obry >>> > declaimed the following in comp.lang.ada: >>> > > I know that the F-22 is 90% of Ada. Is there some public information >>> > > about this bug? Is that a design bug? >> >>> > � � � � So far as I recall -- from some years ago -- it was an algorithm >>> > problem handling position information wrap-around from crossing, as >>> > mentioned, the International Dateline... -180.0 to +180.0 deg longitude. >> >>> > � � � � I didn't hear that they had to follow the tankers back -- was under >>> > the impression once they managed to cross back heading east a reboot of >>> > the navigation system started working again... >> >>> > -- >>> > � � � � Wulfraed � � � � Dennis Lee Bieber � � � � � � � KD6MOG >>> > � � � � wlfr...@ix.netcom.com HTTP://wlfraed.home.netcom.com/ >> >>> For some reason (that I don't get at all) lots of systems define long >>> as -180 <= x <= +180 degrees. >> >>> Having the potential to alias a position seems like a bad idea for a >>> start, so when I've been coding such systems up, I've always spent a >>> bit of time making it convert positions into the range -180 <= x < >>> +180 degrees and using a proper ADT. >> >>> I wonder if it was anything to do with that?... >> >> I would have thought a longitude was really a mod 360, shifted by -180 >> for display purposes? For fractional degrees (i.e. minutes and >> seconds), make that mod (360 * 60 * 60), shift by -180 * 60 * 60 and >> split in degrees, minutes and seconds when displaying. >> >> -- >> Ludovic Brenta. > > No...it's -180 <= x <(=) +180...always - check any map / globe!! > > Lat is always -90 <= x <= +90 deg - no doubt about that one :-) > > Adding "shifts" would make understanding any problem very hard... And shift does not solve the problem anyway, if that existed. The potential problem is that the angle is not a real number. It could be represented by one, but then the operations like +, -, *, /, =, /= must be replaced and ones like <, >, <=, >= disallowed. With that done the value +180 would do no harm, because -180 = +180 in terms of proper ADT operations. You simply would not be able to distinguish them (without tricks like Unchecked_Conversion). -- Regards, Dmitry A. Kazakov http://www.dmitry-kazakov.de