From 445943841274368836 X-Google-Thread: f78e5,1e6093a60facd084 X-Google-Attributes: gidf78e5,public X-Google-Language: ENGLISH,UTF8 Path: g2news2.google.com!news2.google.com!news1.google.com!news.germany.com!feeder.news-service.com!newsgate.cistron.nl!xs4all!news.tele.dk!news.tele.dk!small.news.tele.dk!lnewsinpeer00.lnd.ops.eu.uu.net!emea.uu.net!peer-uk.news.demon.net!kibo.news.demon.net!news.demon.co.uk!demon!stump.algebra.com!devnull From: SeeWebsiteForEmail@erdani.org ("Andrei Alexandrescu (See Website For Email)") Newsgroups: comp.std.c++ Subject: Re: [Proposal] noreturn_t Date: Sun, 5 Nov 2006 03:14:26 GMT Organization: Computer Science & Engineering, U of Washington, Seattle Lines: 63 Sender: mail2news@demon.net Approved: fjh@cs.mu.oz.au (Fergus Henderson , moderator of comp.std.c++) Message-ID: <454D4690.8020709@erdani.org> References: <1161490402.699940.293180@b28g2000cwb.googlegroups.com> <4544215C.4020102@erdani.org> NNTP-Posting-Host: news.news.demon.net Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable X-Trace: news.demon.co.uk 1162697978 3423 158.152.254.254 (5 Nov 2006 03:39:38 GMT) X-Complaints-To: abuse@demon.net NNTP-Posting-Date: Sun, 5 Nov 2006 03:39:38 +0000 (UTC) X-Nntp-Posting-Host: tisbe.cs.washington.edu X-Robomod: STUMP, ichudov@algebra.com (Igor Chudov) X-User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.0.7) Gecko/20060909 Thunderbird/1.5.0.7 Mnenhy/0.7.4.666 X-MIME-Autoconverted: from 8bit to quoted-printable by mulga.csse.unimelb.edu.au id kA53dZhH016707 X-Virus-Scanned: amavisd-new at csse.unimelb.edu.au X-Path: comp-std-cpp-robomod!not-for-mail X-Received: (from fjh@localhost) by mulga.csse.unimelb.edu.au (8.13.6+Sun/8.13.6/Submit) id kA53EQOj012238; Sun, 5 Nov 2006 14:14:26 +1100 (EST) X-Authentication-Warning: mulga.csse.unimelb.edu.au: fjh set sender to devnull@stump.algebra.com using -f X-Newsgroups: comp.std.c++ Xref: g2news2.google.com comp.std.c++:4341 Tommi H=C3=B6yn=C3=A4l=C3=A4nmaa wrote: > Andrei Alexandrescu (See Website For Email) kirjoitti: >> Tommi H=C3=B6yn=C3=A4l=C3=A4nmaa wrote: >>> This is a question about the execution flow and not about the result=20 >>> type of a function. There would be no values whose type is noreturn_t. >>> So "noreturn" should be an attribute of a function like the throw=20 >>> specifications. >> >> The point of the idea was different. Yes, values of that type cannot=20 >> exist, but the properties of the static type control the=20 >> expressiveness of the idioms in which the type could take part. And=20 >> precisely because values of that "none" type can never exist, there is= =20 >> considerable static freedom with regard to the static properties of=20 >> that type, which confers it remarkable expressiveness. >=20 > But isn't "none" roughly equivalent to the void result type in C++? > Function that returns nothing has also a result type that contains no=20 > values. Or does it have some other result type? I think this type shoul= d=20 > also be at the bottom of the type hierarchy. There are similarities between void and none, but also obvious=20 differences. I think we've beaten this horse long enough :o). >>> There could be another attribute "mustreturn" to indicate that a=20 >>> function has to return. "mustreturn" and "noreturn" would be mutually= =20 >>> exclusive. >> >> I guess mustreturn is simply a static incarnation of the nothrow idea.= =20 >> Things get tricky when we start thinking of mustreturn as a guarantee=20 >> that the function doesn't enter infinite loops - it wouldn't generally= =20 >> be quite possible to demonstrate that a function violates that=20 >> assumption :o). >=20 > We could define "mustreturn" e.g. so that > 1) A "mustreturn" function may call only other "mustreturn" functions > or > 2) A "mustreturn" function may not call any "noreturn" functions. > Infinite loops and things like that would not be considered at all. > The semantics of "mustreturn" would be a bit unclear this way because i= t=20 > would be possible that a "mustreturn" function executes an infinite tim= e. >=20 > However, it may be that "mustreturn" is not worth implementing. I also don't think "mustreturn" has much value. For a host of=20 theoretical and practical reasons, "nothrow" is much more worthy=20 focusing on. Andrei --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.comeaucomputing.com/csc/faq.html ]