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-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 103376,f039470e8f537101 X-Google-Attributes: gid103376,public X-Google-ArrivalTime: 2003-07-30 08:04:49 PST Path: archiver1.google.com!news1.google.com!newsfeed.stanford.edu!headwall.stanford.edu!newsfeed.media.kyoto-u.ac.jp!in.100proofnews.com!in.100proofnews.com!news.maxwell.syr.edu!nntp.abs.net!ash.uu.net!spool.news.uu.net!not-for-mail Date: Wed, 30 Jul 2003 11:04:47 -0400 From: Hyman Rosen User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.5a) Gecko/20030611 Thunderbird/0.1a X-Accept-Language: en-us, en MIME-Version: 1.0 Newsgroups: comp.lang.ada Subject: Re: Ariane5 FAQ References: <1058968422.225561@master.nyc.kbcfp.com> <3F200AD0.94F79098@adaworks.com> <7u9Ua.13412$634.10307@nwrdny03.gnilink.net> <3F215120.1040706@attbi.com> <1059151910.357790@master.nyc.kbcfp.com> <3F248CEE.5050709@attbi.com> <3F25FB81.A81694FA@adaworks.com> <3F27C108.14E7000A@adaworks.com> In-Reply-To: <3F27C108.14E7000A@adaworks.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Organization: KBC Financial Products Message-ID: <1059577487.590527@master.nyc.kbcfp.com> Cache-Post-Path: master.nyc.kbcfp.com!unknown@nightcrawler.nyc.kbcfp.com X-Cache: nntpcache 3.0.1 (see http://www.nntpcache.org/) NNTP-Posting-Host: 204.253.250.10 X-Trace: 1059577488 2485 204.253.250.10 Xref: archiver1.google.com comp.lang.ada:41016 Date: 2003-07-30T11:04:47-04:00 List-Id: Richard Riehle wrote: > Yet they did design the Ariane 4 within those limits. > They would have had to anticipate some yet unknown > information regarding future projects. There are two different things here which you are mixing up. The first is making a program work within the limits specified for its external inputs. As you say, Ariane 4 was designed that way, and worked fine. The second is making a program verify that its external inputs actually lie within the specified limits. This was not done in the Ariane 4 case. In general, this is a popular feature to omit, since in a properly functioning overall system, these checks will never trigger. But such programming protects the code against "some yet unknown information regarding future projects" by noticing when specified constraints on external inputs are violated. > There is limit to how much checking one can do in any system. Sure. If the tradeoff was clearly in favor of one side or the other, these discussions woudn't arise as much. It's the same issue as deciding whether to leave range checks turned on in deployed code.