220 8260 <186E0927-C962-4E34-AED0-E7509DD1F0A0@gmail.com> article Path: news.gmane.org!not-for-mail From: Marshall Clow Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: string_view::is_null() Date: Fri, 27 Dec 2013 21:01:34 -0800 Lines: 96 Approved: news@gmane.org Message-ID: <186E0927-C962-4E34-AED0-E7509DD1F0A0@gmail.com> References: <8045a4d2-721d-4725-8bb7-7a91b6f53ec8@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 (Mac OS X Mail 7.1 \(1827\)) Content-Type: multipart/alternative; boundary="Apple-Mail=_18F814F5-564C-478D-85DC-021547C3D448" X-Trace: ger.gmane.org 1388206943 10897 80.91.229.3 (28 Dec 2013 05:02:23 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Sat, 28 Dec 2013 05:02:23 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDHIXP53REBRBYVW7GKQKGQEU5Y2SUQ@isocpp.org Sat Dec 28 06:02:29 2013 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-gg0-f199.google.com ([209.85.161.199]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1Vwm2d-0006Ci-EU for gclcip-std-proposals@m.gmane.org; Sat, 28 Dec 2013 06:02:27 +0100 Original-Received: by mail-gg0-f199.google.com with SMTP id e26sf10808626gga.10 for ; Fri, 27 Dec 2013 21:02:26 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:from:message-id:mime-version:subject:date :references:to:in-reply-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=DZQ76CjKZpTttB6nI/XxzXaByJdN/J19DgglcjJHk6k=; b=iJocP3fmSvx96Fsxzhd0sDBaRieAGoTr98Oiy4KI1Sn30JZTO3j3mrP25SOAkxEOkM dR3mifXt3r3D0Ffxpno+R+dFZ+CCYjkfBWkgOojeFf5yuDEFcuHJjh+ALZMQmeTerx9G gz7LnjxzRXw2bn+VTpVjZsO56y8ROFoMI8PiTTaMkriZfFoi9DQ6cKu6budR56Yj5ZV+ l+WimhHbMoWIywYBJtCT0sizIInBnVzjODjz+fevNFAAFJ6xa3dkZx08QVPdVi7iqMPi hzLYE8vrpmCDSlve23SAPQk64tfh66vBxR0NT19+VVjVjn6/0eBK5P3immWVCe1eibD/ Dh8A== X-Gm-Message-State: ALoCoQnbrd+0hsCdwWx+mszOJMrHW06iVCa72gk02Tbc6m5pUnOnY20r46MvV3RgcdLBi59L+cLd X-Received: by 10.224.55.81 with SMTP id t17mr21067831qag.3.1388206946489; Fri, 27 Dec 2013 21:02:26 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.49.81.229 with SMTP id d5ls2847285qey.64.gmail; Fri, 27 Dec 2013 21:02:26 -0800 (PST) X-Received: by 10.236.152.233 with SMTP id d69mr27473408yhk.11.1388206946006; Fri, 27 Dec 2013 21:02:26 -0800 (PST) Original-Received: from mail-oa0-x229.google.com (mail-oa0-x229.google.com [2607:f8b0:4003:c02::229]) by mx.google.com with ESMTPS id z21si10209291yhb.74.2013.12.27.21.02.25 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Fri, 27 Dec 2013 21:02:26 -0800 (PST) Received-SPF: pass (google.com: domain of mclow.lists@gmail.com designates 2607:f8b0:4003:c02::229 as permitted sender) client-ip=2607:f8b0:4003:c02::229; Original-Received: by mail-oa0-f41.google.com with SMTP id j17so10510237oag.0 for ; Fri, 27 Dec 2013 21:02:25 -0800 (PST) X-Received: by 10.182.194.5 with SMTP id hs5mr36520656obc.19.1388206945538; Fri, 27 Dec 2013 21:02:25 -0800 (PST) Original-Received: from [192.168.16.50] (wsip-174-77-164-131.sd.sd.cox.net. [174.77.164.131]) by mx.google.com with ESMTPSA id qh4sm44040298obc.4.2013.12.27.21.02.23 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Fri, 27 Dec 2013 21:02:23 -0800 (PST) In-Reply-To: <8045a4d2-721d-4725-8bb7-7a91b6f53ec8@isocpp.org> X-Mailer: Apple Mail (2.1827) X-Original-Sender: mclow.lists@gmail.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of mclow.lists@gmail.com designates 2607:f8b0:4003:c02::229 as permitted sender) smtp.mail=mclow.lists@gmail.com; dkim=pass header.i=@gmail.com; dmarc=pass (p=NONE dis=NONE) header.from=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:8260 Archived-At: --Apple-Mail=_18F814F5-564C-478D-85DC-021547C3D448 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=windows-1252 On Dec 27, 2013, at 4:52 AM, abolz.lists@gmail.com wrote: > Is there a reason why string_view is not nullable? >=20 > Nullable here means default constructed or constructed from a nullptr > (and a zero length). Then adding a is_null() (or null()) member > function which can then be used to distinguish the string_view from an > empty string. i think that attempting to distinguish between an empty string_view that = =93used to point at something=94 and an empty string view =93that never pointed at anything=94 is a use case= to be discouraged, rather than something that should be enshrined in the standard. > This should not affect data() which returns a non-null pointer. >=20 I disagree here with the proposal as currently written. I believe that the requirement that data() always return a non-null pointer= is misguided. if sv.size () =3D=3D 0 or sv.empty () [same thing], there is nothing that y= ou can do with sv.data() (except compare it to null, and that doesn=92t tell you anything useful). An empty string view need not point *anywhere*, or have any data behind it. =97 Marshall P.S. In my implementation, I=92m tempted to have a default-constructed stri= ng_view return a value of 1 from data(). --=20 ---=20 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 e= mail 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-proposa= ls/. --Apple-Mail=_18F814F5-564C-478D-85DC-021547C3D448 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=windows-1252 On Dec 27, 2013, at 4:= 52 AM, abolz.lists@gmail.com w= rote:

Is there a reason why string_view is not nullable?=

Nullable here means default constructed or constructed from a= nullptr
(and a zero length). Then adding a is_null() (or null())= member
function which can then be used to distinguish the string= _view from an
empty string.

i think that attempting to distinguish between an empty string_view that = =93used to point at something=94
and an empty string view =93that= never pointed at anything=94 is a use case to be discouraged, rather than<= /div>
something that should be enshrined in the standard.

This should not a= ffect data() which returns a non-null pointer.

=
I disagree here with the proposal as currently written.
I believe that the requirement that data() always return a non-null pointe= r is misguided.

if sv.size () =3D=3D 0 or sv= ..empty () [same thing], there is nothing that you can do with sv.data()
(except compare it to null, and that doesn=92t tell you anything use= ful).

An empty string view need not point *anywher= e*, or have any data behind it.

=97 Marshall
=

P.S. In my implementation, I=92m tempted to have a default-co= nstructed string_view return a value of 1 from data().

=

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