220 2365 article Path: news.gmane.org!not-for-mail From: Daniel James Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: optional, one more value or two states Date: Sun, 27 Jan 2013 21:27:34 +0000 Lines: 41 Approved: news@gmane.org Message-ID: References:

<2c2b9360-8e5e-422d-9b85-124bd947b004@isocpp.org> <123b9f65-12fd-4285-bb6c-cfee383d4552@isocpp.org>

Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 X-Trace: ger.gmane.org 1359322054 30621 80.91.229.3 (27 Jan 2013 21:27:34 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Sun, 27 Jan 2013 21:27:34 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCGPB3VVUAGBBR5XS2EAKGQE3HE6YSQ@isocpp.org Sun Jan 27 22:27:53 2013 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-wg0-f72.google.com ([74.125.82.72]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1TzZlZ-0005d5-75 for gclcip-std-proposals@m.gmane.org; Sun, 27 Jan 2013 22:27:53 +0100 Original-Received: by mail-wg0-f72.google.com with SMTP id fg15sf2172871wgb.7 for ; Sun, 27 Jan 2013 13:27:35 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=x-received:x-beenthere:x-received:x-received:received-spf :mime-version:x-received:in-reply-to:references:date:message-id :subject:from:to:x-original-sender:x-original-authentication-results :reply-to:precedence:mailing-list:list-id:x-google-group-id :list-post:list-help:list-archive:list-subscribe:list-unsubscribe :content-type; bh=exAxUyzvxswIcVFGlMC4eaILeDijhXrsWT6mrOFjK6I=; b=KOBO6WeuzjLbKXV6/SpEAYqb58bv1hKlGwNU8ZsaCJlDIgnd/K4VC7uBUBDSrS/rfQ yG1v/DYTG7cFG5p4UwCt1UyR5Xra8+Xa8EnRn+o2VArYckgeuAP5/d+0aqfeXn0sTPV+ A3K4PUm80bfOp89qILxt86CKt7PeKMGh11BG48kgti1J/eKqRfK72PqmTNCqq6dqL0lH cyJtV0v5t6xyJRGWyKb9kBZsvciWrzCqThMgLa/DzDPNeNKPSY6qeuxKE7TD+5LMPY4S m3V3bUa1YzyVBUlPTrE+9cEVonDN9LcZ5iOga9lWM0FK7kobG X-Received: by 10.180.105.39 with SMTP id gj7mr37244wib.0.1359322055377; Sun, 27 Jan 2013 13:27:35 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.180.90.200 with SMTP id by8ls783613wib.6.gmail; Sun, 27 Jan 2013 13:27:34 -0800 (PST) X-Received: by 10.180.109.195 with SMTP id hu3mr6355077wib.31.1359322054728; Sun, 27 Jan 2013 13:27:34 -0800 (PST) X-Received: by 10.180.109.195 with SMTP id hu3mr6355076wib.31.1359322054703; Sun, 27 Jan 2013 13:27:34 -0800 (PST) Original-Received: from mail-wi0-f178.google.com (mail-wi0-f178.google.com [209.85.212.178]) by mx.google.com with ESMTPS id e1si2740682wjb.14.2013.01.27.13.27.34 (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Sun, 27 Jan 2013 13:27:34 -0800 (PST) Received-SPF: pass (google.com: domain of dnljms@gmail.com designates 209.85.212.178 as permitted sender) client-ip=209.85.212.178; Original-Received: by mail-wi0-f178.google.com with SMTP id hn3so920986wib.17 for ; Sun, 27 Jan 2013 13:27:34 -0800 (PST) X-Received: by 10.180.109.10 with SMTP id ho10mr6492827wib.9.1359322054621; Sun, 27 Jan 2013 13:27:34 -0800 (PST) Original-Received: by 10.194.46.7 with HTTP; Sun, 27 Jan 2013 13:27:34 -0800 (PST) In-Reply-To: X-Original-Sender: dnljms@gmail.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of dnljms@gmail.com designates 209.85.212.178 as permitted sender) smtp.mail=dnljms@gmail.com; dkim=pass header.i=@gmail.com Precedence: list Mailing-list: list std-proposals@isocpp.org; contact std-proposals+owners@isocpp.org List-ID: X-Google-Group-Id: 399137483710 List-Post: , List-Help: , List-Archive: List-Subscribe: , List-Unsubscribe: , Xref: news.gmane.org gmane.comp.lang.c++.isocpp.proposals:2365 Archived-At: On 27 January 2013 20:55, Ville Voutilainen wrote: > Yes? x and y point to different things also if y is of the proposed > value_ptr type. Don't you think it's odd that value_ptr doesn't behave like a pointer? That's because it isn't a pointer, it's a fixed size container (like array). Calling it 'value_ptr' is like referring to 'std::vector' as 'value_ptr_with_length' - it's the implementation not the interface. > They point to different things if y is an auto_ptr. I'd forgotten about auto_ptr, but since it is deprecated, it's largely irrelevant. I think everyone agrees that auto_ptr is not an example of good design. IMO it actually supports my principle. The problem with auto_ptr is that it doesn't follow the expected semantics. > So there are > already exceptions > to this alleged rule, and chances are there's more exceptions coming. IMO there shouldn't be. Thanks to templates, C++ has an odd mix of structural and nominal typing. So when you have a type structure the implies a certain behaviour, it means something. I don't think saving a few characters is a good reason to break that. Anyone who does think that it is should at least acknowledge that there is a trade off here. Some people have referred to optional as a "nullable proxy". But it isn't a proxy, it's a container (in the sense that it contains things, not in the sense of the C++ definition - although it should be, for things like flatMap). -- --- You received this message because you are subscribed to the Google Groups "ISO C++ Standard - Future Proposals" group. To post to this group, send email to std-proposals@isocpp.org. To unsubscribe from this group, send email to std-proposals+unsubscribe@isocpp.org. Visit this group at http://groups.google.com/a/isocpp.org/group/std-proposals/?hl=en. .