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,FREEMAIL_FROM autolearn=ham autolearn_force=no version=3.4.4 X-Google-Thread: 103376,37e5589e32d8f03f X-Google-Attributes: gid103376,public X-Google-Language: ENGLISH,ASCII-7-bit Path: g2news1.google.com!news2.google.com!proxad.net!134.158.69.22.MISMATCH!in2p3.fr!kanaga.switch.ch!switch.ch!newsfeed00.sul.t-online.de!newsmm00.sul.t-online.de!t-online.de!news.t-online.com!not-for-mail From: Matthias Kretschmer Newsgroups: comp.lang.ada Subject: Re: Floating-Point Numbers and Internal Representation Date: Sun, 4 Dec 2005 22:16:42 +0100 Organization: T-Online Message-ID: References: <1843142.NoXPLYbHQs@linux1.krischik.com> <4fnetd7d1gzw$.6esjklahq38$.dlg@40tude.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit X-Trace: news.t-online.com 1133731002 03 12840 qVhyJiN19mlF6pG 051204 21:16:42 X-Complaints-To: usenet-abuse@t-online.de X-ID: E6O54iZpZeIzGXkw-+wV7xTY8QiLA8ApxG0-xqnAlzTqH6Ze9dJdwy User-Agent: slrn/0.9.8.1 (NetBSD) Xref: g2news1.google.com comp.lang.ada:6740 Date: 2005-12-04T22:16:42+01:00 List-Id: On 2005-12-04, Dmitry A. Kazakov wrote: > On Sun, 4 Dec 2005 16:15:31 +0100, Matthias Kretschmer wrote: > >> as I hope I said in my original posting, I am very well aware of this, >> but I had this special case where I wanted to use explicitly equality. >> There are times, when one is sure, that even with rounding errors, the >> two compared floating point numbers are really equal or not if one is >> using some good enough precision. So from some defined point on all >> following digits can be considered garbage, as it was in my case. > > This is exactly definition of an interval: [xx.xxx0(0), xx.xxxx9(9)] > >> The >> best solution would be that I had used Q (or a fixed subset of it) >> instead an approximation of R for my calculations, but I was too lazy :) > > No, this contradicts to your statement about "following digits" being > garbage. In the case of Q they are not. ah well - as long as you know you have no periodical numbers, it doesn't matter. > >> Maybe I should take the time and port it to such a solution or implement >> something like that myself. At least in many circumstances using exact >> numbers instead of unexact ones causes much less trouble :) > > Ah but this is a completely different story. If you *really* know that > multiplication and division are exact then Ada's fixed point types is just > what you need. Fixed point numbers are perfectly comparable. > hmm you're right. Forgot about this. Thanks for the hint. Didn't do stuff in Ada for a long time, I think I forgot most of the stuff. -- Matthias Kretschmer