220 2259 article Path: news.gmane.org!not-for-mail From: Tony V E Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: optional, one more value or two states Date: Fri, 25 Jan 2013 11:05:06 -0500 Lines: 56 Approved: news@gmane.org Message-ID: References:

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 1359129913 4386 80.91.229.3 (25 Jan 2013 16:05:13 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Fri, 25 Jan 2013 16:05:13 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCUZ5QWKNQILFWUKRACRUBEXC3M5Y@isocpp.org Fri Jan 25 17:05:31 2013 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-vc0-f198.google.com ([209.85.220.198]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1TylmO-0007E7-RB for gclcip-std-proposals@m.gmane.org; Fri, 25 Jan 2013 17:05:25 +0100 Original-Received: by mail-vc0-f198.google.com with SMTP id m8sf635636vcd.1 for ; Fri, 25 Jan 2013 08:05:06 -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=RZJ8RR+Z5Awr4+LBLMst8kV1r3r9H9DLJT3CNSlYoqA=; b=K3G8NgeWdA+3FzUkrL/SWEs2DCgPZ60w+ELgkeGLibbhG64VHR1NNq5pWl5BqkUqyb atfhRJQJJeyu0JLcYqy22SS1v/yaGPdes9lShyiJ4HowXy4PdHH8XtF2GTFNdCfJxObh FsTH+2p37+m+XkAL94WtutgbJ8CcSWah//6sJKqr/kcSKPz3KfIyrwL8ABnPb6cGAsBt /wl/dg9DTrZoGOLzepHkxYZlvGsOGBGOEVJGTPPE7ynT0+wFow0ML38TmLhdEbYlU3di JpYtsXtocyueEElpFB6QgPrOYaXYq4EY8Myf/Gr/NQIH4QIyj X-Received: by 10.236.152.6 with SMTP id c6mr1909886yhk.21.1359129906845; Fri, 25 Jan 2013 08:05:06 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.49.82.19 with SMTP id e19ls203090qey.38.gmail; Fri, 25 Jan 2013 08:05:06 -0800 (PST) X-Received: by 10.224.39.210 with SMTP id h18mr6392698qae.15.1359129906535; Fri, 25 Jan 2013 08:05:06 -0800 (PST) X-Received: by 10.224.39.210 with SMTP id h18mr6392697qae.15.1359129906519; Fri, 25 Jan 2013 08:05:06 -0800 (PST) Original-Received: from mail-qc0-f173.google.com (mail-qc0-f173.google.com [209.85.216.173]) by mx.google.com with ESMTPS id w5si406996qct.101.2013.01.25.08.05.06 (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Fri, 25 Jan 2013 08:05:06 -0800 (PST) Received-SPF: pass (google.com: domain of tvaneerd@gmail.com designates 209.85.216.173 as permitted sender) client-ip=209.85.216.173; Original-Received: by mail-qc0-f173.google.com with SMTP id b12so258187qca.18 for ; Fri, 25 Jan 2013 08:05:06 -0800 (PST) X-Received: by 10.49.12.138 with SMTP id y10mr7273592qeb.64.1359129906276; Fri, 25 Jan 2013 08:05:06 -0800 (PST) Original-Received: by 10.49.87.168 with HTTP; Fri, 25 Jan 2013 08:05:06 -0800 (PST) In-Reply-To: X-Original-Sender: tvaneerd@gmail.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of tvaneerd@gmail.com designates 209.85.216.173 as permitted sender) smtp.mail=tvaneerd@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:2259 Archived-At: On Fri, Jan 25, 2013 at 1:55 AM, Nicol Bolas wrote: > > > On Thursday, January 24, 2013 8:56:08 PM UTC-8, Tony V E wrote: >> >> On Thu, Jan 24, 2013 at 7:10 PM, Dean Michael Berris >> wrote: >> > >> > In my opinion: >> > >> > - There's a precedent in other languages for a ".get(default_value)". >> > Why don't we have this for optional instead? >> > >> >> opt.get(17) doesn't look like it is using a default to me. Typically >> get(17) is get the 17th element or lookup with key = 17, etc. >> >> >> > - Why are we forcing pointer semantics on optional? Maybe there's a >> > different concept here at play. >> > >> >> Because much of optional's interface is similar to pointers: you >> access the value with *opt and opt can be NULL. >> >> That is the essential "problem" with optional. Sometimes it acts >> value-ish, sometimes pointer-ish. It is like quantum physics - >> sometimes a particle, sometimes a wave... > > > But it doesn't act like a pointer. Indeed, the *only* thing "pointer-ish" > about it is that it has an `operator*`. In every other way, it acts like a > value. And can be NULL. It has value semantics, for the most part (ie besides the null), but pointer syntax. That's not necessarily wrong, but I do think it is and the heart of many of the questions/issues. > > If it helps limit confusion, we could get rid of `operator*`. > -- --- 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. .