220 8729 article Path: news.gmane.org!not-for-mail From: Nevin Liber Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: string_view::is_null() Date: Mon, 20 Jan 2014 00:25:58 -0600 Lines: 78 Approved: news@gmane.org Message-ID: References: <104254A6-C69A-4571-8455-89D7E466D493@gmail.com> <6a95bf9c-55c9-4ae2-966f-d1b1f4df6a37@isocpp.org> <52D9E336.1060801@knejp.de> <1B534FD7-B385-4A7E-A718-3C73F0AB61DC@gmail.com> <11f13f8f-1270-427c-8942-94027a181ff4@isocpp.org> <20140119174431.GA16875@faust.lysator.liu.se> <20140119192238.GA19497@faust.lysator.liu.se> <60842af6-5ec4-4364-b2d5-a0be9d578bd6@isocpp.org> <6c82c4ae-c144-443a-81b2-ea1a6b645601@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary=f46d043c7de66b9a3f04f060f977 X-Trace: ger.gmane.org 1390199192 25887 80.91.229.3 (20 Jan 2014 06:26:32 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Mon, 20 Jan 2014 06:26:32 +0000 (UTC) To: "std-proposals@isocpp.org" Original-X-From: std-proposals+bncBCE35H5S6IDBBH4D6OLAKGQEWMLYV4I@isocpp.org Mon Jan 20 07:26:40 2014 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-wi0-f200.google.com ([209.85.212.200]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1W58Jk-0001pW-AY for gclcip-std-proposals@m.gmane.org; Mon, 20 Jan 2014 07:26:40 +0100 Original-Received: by mail-wi0-f200.google.com with SMTP id ex4sf5723526wid.7 for ; Sun, 19 Jan 2014 22:26:39 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:sender:in-reply-to:references:from :date:message-id:subject:to:x-original-sender :x-original-authentication-results:reply-to:precedence:mailing-list :list-id:list-post:list-help:list-archive:list-subscribe :list-unsubscribe:content-type; bh=BgrSpzljLOP5fq9M7pYkIEIW2KUoe+Rm1tGvmHw5OA0=; b=XdGnwxMEmg/NVHtSZjWeBJPj57IHBAyOMk29sURglcG0eNVA3tk2NgNmuRdHnRO2vd qfCqyyC46H89z7ezdguh9rmVxrlny+13RAR1xRMTTHM2blSBxgg9eTCcrHqNj6BUAsan hSNTx6ZIHiy5f2zMd/dAthP0ktTeoC+z3PaezwnTk4pxViQvcjA+HsJUKopW3LORPoVr M3da3FuITXaUEhqmYt0gYPuXpOcbRkrdTeAd1rr0p08bBWuwKeaNnwDkw8/3GuG5y7mC LBmi5GpaF3LvnAX465EZyq1UxRSecDicSExWQasoZM57f4cH/8nY6ozeJJC/l+ilfWac DQyA== X-Gm-Message-State: ALoCoQkGr/BsSl8mWt8lrykHrErY1GCY0cOorDnr5WRK0fS/rX7Ne7vnow7ofLV+E3sA2eJuiu8e X-Received: by 10.180.228.166 with SMTP id sj6mr5714162wic.2.1390199199774; Sun, 19 Jan 2014 22:26:39 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.181.12.101 with SMTP id ep5ls406141wid.40.gmail; Sun, 19 Jan 2014 22:26:39 -0800 (PST) X-Received: by 10.180.76.42 with SMTP id h10mr8544049wiw.46.1390199199160; Sun, 19 Jan 2014 22:26:39 -0800 (PST) Original-Received: from mail-we0-x22f.google.com (mail-we0-x22f.google.com [2a00:1450:400c:c03::22f]) by mx.google.com with ESMTPS id em6si156626wib.36.2014.01.19.22.26.39 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Sun, 19 Jan 2014 22:26:39 -0800 (PST) Received-SPF: pass (google.com: domain of nliber@gmail.com designates 2a00:1450:400c:c03::22f as permitted sender) client-ip=2a00:1450:400c:c03::22f; Original-Received: by mail-we0-f175.google.com with SMTP id p61so6436332wes.6 for ; Sun, 19 Jan 2014 22:26:39 -0800 (PST) X-Received: by 10.181.13.11 with SMTP id eu11mr8342052wid.30.1390199198946; Sun, 19 Jan 2014 22:26:38 -0800 (PST) Original-Sender: nliber@gmail.com Original-Received: by 10.194.121.163 with HTTP; Sun, 19 Jan 2014 22:25:58 -0800 (PST) In-Reply-To: X-Original-Sender: nevin@eviloverlord.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of nliber@gmail.com designates 2a00:1450:400c:c03::22f as permitted sender) smtp.mail=nliber@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:8729 Archived-At: --f46d043c7de66b9a3f04f060f977 Content-Type: text/plain; charset=ISO-8859-1 On 20 January 2014 00:12, Jeffrey Yasskin wrote: > > My personal preference for all this is that string_view(nullptr, 0) be > > allowed, and it is a Quality of Implementation issue whether or not > > sv.data() can ever return a nullptr; i.e., it would be allowed to return > any > > legal pointer it wants for an empty string_view. > > That's interesting. It's easier to both specify and implement to just > say that string_view(x, y).data()==x and string_view(x, y).size()==y, > assuming [x, x+y) is a valid range. Why would you special-case data() > to return arbitrary things when y==0? > A debugging implementation may want to ensure that developers aren't dependent on "knowing" that a nullptr was passed in. -- Nevin ":-)" Liber (847) 691-1404 -- --- You received this message because you are subscribed to the Google Groups "ISO C++ Standard - Future Proposals" group. To unsubscribe from this group and stop receiving emails from it, send an email to std-proposals+unsubscribe@isocpp.org. To post to this group, send email to std-proposals@isocpp.org. Visit this group at http://groups.google.com/a/isocpp.org/group/std-proposals/. --f46d043c7de66b9a3f04f060f977 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
On 20 January 2014 00:12, Jeffrey Yasskin <jyasskin@goo= gle.com> wrote:
> My personal preferenc= e for all this is that string_view(nullptr, 0) be
> allowed, and it is a Quality of Implementation issue whether or not > sv.data() can ever return a nullptr; i.e., it would be allowed to retu= rn any
> legal pointer it wants for an empty string_view.

That's interesting. It's easier to both specify and implement= to just
say that string_view(x, y).data()=3D=3Dx and string_view(x, y).size()=3D=3D= y,
assuming [x, x+y) is a valid range. Why would you special-case data()
to return arbitrary things when y=3D=3D0?

A debugging implementation may want to ensure that developers aren't= dependent on "knowing" that a nullptr was passed in.
--
=A0Nevin ":-)" Liber=A0 <mailto:nevin@eviloverlord.com>=A0 (847= ) 691-1404

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