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 Path: border1.nntp.dca3.giganews.com!backlog3.nntp.dca3.giganews.com!border2.nntp.dca.giganews.com!nntp.giganews.com!newspeer1.nac.net!newsfeed.xs4all.nl!newsfeed1a.news.xs4all.nl!xs4all!news.stack.nl!aioe.org!.POSTED!not-for-mail From: "Dmitry A. Kazakov" Newsgroups: comp.lang.ada Subject: Re: OT: A bit of Sudoku Date: Fri, 13 Jun 2014 14:37:39 +0200 Organization: cbb software GmbH Message-ID: <1dyqwgwxr6juq.183jmdfiehbb0$.dlg@40tude.net> References: <5365d3f0-43cc-47ef-989c-d47992c84c9f@googlegroups.com> <3ar2JRBR4smTFwAN@ada-augusta.demon.co.uk> Reply-To: mailbox@dmitry-kazakov.de NNTP-Posting-Host: QTaafVZuunHujkJPndFR7g.user.speranza.aioe.org Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit X-Complaints-To: abuse@aioe.org User-Agent: 40tude_Dialog/2.0.15.1 X-Notice: Filtered by postfilter v. 0.8.2 X-Original-Bytes: 2279 Xref: number.nntp.dca.giganews.com comp.lang.ada:186892 Date: 2014-06-13T14:37:39+02:00 List-Id: On Fri, 13 Jun 2014 11:10:25 +0100, Mike H wrote: > In message , Shark8 > writes >> >> -- Definition of "=" returns true when both sides are NULL, >> -- returns false when only one side is NULL, and behaves as >> -- normal string-equality when neither side is NULL. > Is this an example where Dmitry's three state logical (True, Uncertain, > False) might be useful? > See As much as I wished, I can take credit for tri-state logic. It was known since first third of XX century. The extension is four-state Dunn-Belnap's logic (true, false, uncertain, contradictory), of which natural application is for run-time check conditions. [*] Run-time checks could be inconsistent, e.g. when two sources contradict each other. A trustful (AKA gullibility) combination of the sources (say from two independent packages) yields "contradictory". A conservative (AKA consensus) combination does "uncertain". Interval relation use only conservative combination, thus tri-state logic is sufficient for them. ---------------- * Reasoning based on lies, so to say. -- Regards, Dmitry A. Kazakov http://www.dmitry-kazakov.de