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,FREEMAIL_FROM, REPLYTO_WITHOUT_TO_CC autolearn=no autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 103376,c42dbf68f5320193 X-Google-Attributes: gid103376,public X-Google-ArrivalTime: 2002-05-07 14:10:12 PST Path: archiver1.google.com!news1.google.com!newsfeed.stanford.edu!logbridge.uoregon.edu!elk.ncren.net!nntp.upenn.edu!msunews!not-for-mail From: "Chad R. Meiners" Newsgroups: comp.lang.ada Subject: Turing-undecidable languages (OT) Date: Tue, 7 May 2002 17:05:50 -0400 Organization: Michigan State University Message-ID: References: <7mWB8.6827$0z6.115522658@newssvr21.news.prodigy.com> Reply-To: "Chad R. Meiners" NNTP-Posting-Host: arctic.cse.msu.edu X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 6.00.2600.0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2600.0000 Xref: archiver1.google.com comp.lang.ada:23677 Date: 2002-05-07T17:05:50-04:00 List-Id: wrote in message news:7mWB8.6827$0z6.115522658@newssvr21.news.prodigy.com... > If someone says "I'll write a program to do such and such", how should > he act differently if told: > a) that's recursively undecidable > or > b) your program may get stuck in an infinite loop This is an excellent question. First, let's rephrase your question to: If some says, "I'll am going to write a program Y that solves problem X", how should he act if told a) X is not recursive. (This is the same as Robert's recursively undecidable) b) Program Y may get stuck in an infinite loop. In case a, Y cannot exist. Case b depends solely on what you meant by "may get stuck in an infinite loop". In fact the pragmatics of b can either be X is recursive or X is not recursive. So the only thing the programmer can do if told b is ask for clarification. -CRM