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=0.4 required=5.0 tests=BAYES_00,FORGED_MUA_MOZILLA autolearn=no autolearn_force=no version=3.4.4 X-Google-Thread: 103376,ab1d177a5a26577d X-Google-NewGroupId: yes X-Google-Attributes: gida07f3367d7,domainid0,public,usenet X-Google-Language: ENGLISH,UTF8 Received: by 10.68.27.230 with SMTP id w6mr10336428pbg.3.1317790126792; Tue, 04 Oct 2011 21:48:46 -0700 (PDT) Path: lh7ni11857pbb.0!nntp.google.com!news1.google.com!goblin2!goblin.stu.neva.ru!aioe.org!news.tornevall.net!.POSTED!not-for-mail From: Jeffrey Carter Newsgroups: comp.lang.ada Subject: Re: What's wrong with C++? Date: Tue, 04 Oct 2011 21:48:43 -0700 Organization: TornevallNET - http://news.tornevall.net Message-ID: References: <1ee1a434-4048-48f6-9f5e-d8126bebb808@r19g2000prm.googlegroups.com> NNTP-Posting-Host: 58e259e909821ab248d116378e35e660 Mime-Version: 1.0 X-Trace: b811f7f248eb042376e617d2b203bb7f X-Complaints-To: abuse@tornevall.net User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.23) Gecko/20110922 Thunderbird/3.1.15 X-Complaints-Language: Spoken language is english or swedish - NOT ITALIAN, FRENCH, GERMAN OR ANY OTHER LANGUAGE! In-Reply-To: X-UserIDNumber: 1738 X-Validate-Post: http://news.tornevall.net/validate.php?trace=b811f7f248eb042376e617d2b203bb7f X-Complaints-Italiano: Non abbiamo padronanza della lingua italiana - se mandate una email scrivete solo in Inglese, grazie X-Posting-User: 0243687135df8c4b260dd4a9a93c79bd Xref: news1.google.com comp.lang.ada:18304 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Date: 2011-10-04T21:48:43-07:00 List-Id: On 10/04/2011 07:13 PM, Yannick Duchêne (Hibou57) wrote: > Le Wed, 05 Oct 2011 03:53:28 +0200, Peter C. Chapin a écrit: >> I don't think this is a big deal. It's an interesting theoretical >> observation with little practical significance. > Bad theoretical background is no good (at least, it matters to me, to me, it is > a base of trustability). Most people misunderstand the halting problem, thinking it proves that it is impossible to prove whether a program halts. In fact, it says it's impossible to write a program that, in finite time, can say whether any possible program halts for all inputs. It does not say it's impossible to write a program that can say whether a specific program halts for all inputs, or whether a subset of programs halt for all inputs. In fact, there are programs now that can prove whether most sequential programs halt for all inputs. See the article "Proving Program Termination" by Cook, Podelski, and Rybalchenko in the 2011 May /Communications of the ACM/ for an overview of current work on this subject. These programs can, in finite time, return Terminates, Doesn't Terminate, or Unknown, on real code of reasonable size, with Unknown returned infrequently enough that the programs are useful in practice. So I agree that the Turing completeness of C++ templates is unlikely to be a problem for real-world programs. -- Jeff Carter "I was hobbling along, minding my own business, all of a sudden, up he comes, cures me! One minute I'm a leper with a trade, next minute my livelihood's gone! Not so much as a 'by your leave!' You're cured, mate. Bloody do-gooder!" Monty Python's Life of Brian 76