From 870640093501462725 X-Google-Thread: f78e5,1e6093a60facd084 X-Google-Attributes: gidf78e5,public X-Google-Language: ENGLISH,UTF8 Path: g2news2.google.com!news3.google.com!newsfeed2.dallas1.level3.net!news.level3.com!newsfeed-00.mathworks.com!peer-uk.news.demon.net!kibo.news.demon.net!news.demon.co.uk!demon!stump.algebra.com!devnull From: tommi.hoynalanmaa@iki.fi (=?UTF-8?B?VG9tbWkgSMO2eW7DpGzDpG5tYWE=?=) Newsgroups: comp.std.c++ Subject: Re: [Proposal] noreturn_t Date: Sun, 5 Nov 2006 00:51:33 GMT Organization: Saunalahti Customer Lines: 53 Sender: mail2news@demon.net Approved: fjh@cs.mu.oz.au (Fergus Henderson , moderator of comp.std.c++) Message-ID: 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 1162688981 13509 158.152.254.254 (5 Nov 2006 01:09:41 GMT) X-Complaints-To: abuse@demon.net NNTP-Posting-Date: Sun, 5 Nov 2006 01:09:41 +0000 (UTC) X-Original-To: std-c++@mailman.ucar.edu X-Robomod: STUMP, ichudov@algebra.com (Igor Chudov) X-User-Agent: Thunderbird 1.5.0.7 (X11/20060922) X-MIME-Autoconverted: from 8bit to quoted-printable by mulga.csse.unimelb.edu.au id kA519agh015691 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 kA50pXJ9012619; Sun, 5 Nov 2006 11:51:33 +1100 (EST) X-NNTP-Posting-Date: Sat, 04 Nov 2006 22:18:39 EET X-Delivered-To: std-c++@mailman.ucar.edu 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++:4335 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. >=20 > The point of the idea was different. Yes, values of that type cannot=20 > exist, but the properties of the static type control the expressiveness= =20 > of the idioms in which the type could take part. And precisely because=20 > values of that "none" type can never exist, there is considerable stati= c=20 > freedom with regard to the static properties of that type, which confer= s=20 > it remarkable expressiveness. 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 should=20 also be at the bottom of the type hierarchy. >> There could be another attribute "mustreturn" to indicate that a=20 >> function has to return. "mustreturn" and "noreturn" would be mutually=20 >> exclusive. >=20 > 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). 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 it=20 would be possible that a "mustreturn" function executes an infinite time. However, it may be that "mustreturn" is not worth implementing. --=20 Tommi H=C3=B6yn=C3=A4l=C3=A4nmaa s=C3=A4hk=C3=B6posti / e-mail: tommi.hoynalanmaa@iki.fi kotisivu / homepage: http://www.iki.fi/tohoyn/ --- [ 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 ]