220 8280 <5f119e75-8d40-4cb1-b25d-778b1bbc88a5@isocpp.org> article Path: news.gmane.org!not-for-mail From: Peter Bigot Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: string_view::is_null() Date: Sat, 28 Dec 2013 11:27:52 -0800 (PST) Lines: 110 Approved: news@gmane.org Message-ID: <5f119e75-8d40-4cb1-b25d-778b1bbc88a5@isocpp.org> References: <8045a4d2-721d-4725-8bb7-7a91b6f53ec8@isocpp.org> <186E0927-C962-4E34-AED0-E7509DD1F0A0@gmail.com> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_1283_28188992.1388258872556" X-Trace: ger.gmane.org 1388258867 2955 80.91.229.3 (28 Dec 2013 19:27:47 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Sat, 28 Dec 2013 19:27:47 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDA3LUEAQACBBOOM7SKQKGQEONCPTQQ@isocpp.org Sat Dec 28 20:27:55 2013 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-ie0-f199.google.com ([209.85.223.199]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1VwzYA-0001mm-Im for gclcip-std-proposals@m.gmane.org; Sat, 28 Dec 2013 20:27:54 +0100 Original-Received: by mail-ie0-f199.google.com with SMTP id lx4sf48506546iec.10 for ; Sat, 28 Dec 2013 11:27:53 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:date:from:to:message-id:in-reply-to:references :subject:mime-version:x-original-sender:reply-to:precedence :mailing-list:list-id:list-post:list-help:list-archive :list-subscribe:list-unsubscribe:content-type; bh=XEIsjvpsLqHKBMUb/KQnkZmwkMA5Fx9ijhrBvhLD3kY=; b=iBKzSjh5DcijskrlFhmST6ovLXdf+VTNf3ns4ST6r5jzp/kwYox5T1N4K5voMcF+rI NLgYYuOQ695v56ExbfBEIt1+ghYiR7gicI5VsK7ycF7K3/L63sIMMwD/SNRa5+U7Uuob /LJBULzjZSk2BIFBpYsSKR97swjWA7IV8CuT9fIsJLalyvQOopSQlU7rWXQEGptQm057 DlORM7oR+Ngq168VddHdl8569YAQby2T2KdYnlm1nAX4rCtCPUBehHcwCLFcY2EwHYUD 1Fw4NtnN/jbDvYazM6ilYZ1rqniRTVO9KvZ9yYvmo+ZHrTj5Eh+jd/uw4tAP1cWH86l3 O9yw== X-Gm-Message-State: ALoCoQkOPKzkOpx9Kp9j5Hly4jPs2aIrCqGdcBNUGR0Y04hs9IFJWT7iMg24l2503Jo5eIk8ojKd X-Received: by 10.43.74.133 with SMTP id yw5mr18570866icb.15.1388258873685; Sat, 28 Dec 2013 11:27:53 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.182.191.103 with SMTP id gx7ls1321384obc.25.gmail; Sat, 28 Dec 2013 11:27:53 -0800 (PST) X-Received: by 10.182.96.135 with SMTP id ds7mr476376obb.1.1388258873006; Sat, 28 Dec 2013 11:27:53 -0800 (PST) In-Reply-To: X-Original-Sender: bigotp@acm.org 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:8280 Archived-At: ------=_Part_1283_28188992.1388258872556 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable On Saturday, December 28, 2013 1:21:12 PM UTC-6, Peter Bigot wrote: > > > On Friday, December 27, 2013 11:01:34 PM UTC-6, Marshall wrote: >> >> >> if sv.size () =3D=3D 0 or sv.empty () [same thing], there is nothing tha= t you=20 >> can do with sv.data() >> (except compare it to null, and that doesn=92t tell you anything useful)= .. >> > > My understanding (which I'd like confirmed) is that sv.data() is still=20 > useful as it provides a valid position within the referenced object, whic= h=20 > might be referenced by other string_view instances or in its native form. > > Thus, for example, a function object conforming to the delimiters=20 > interface documented at=20 > http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3593.html#delimi= tersmight return a zero-length string to denote a zero-length delimiter (e.= g.,=20 > the position following a period in an English sentence). In this case it= =20 > is the value of sv.data() that tells the caller where the delimited=20 > sequence ends and the next sequence begins. > > Sorry; I misread the details of that proposal: it explicitly uses an empty= =20 delimiter to indicate "not found" (too bad; zero-length delimiters would be= =20 useful). It does, though, specify "not found" as an empty string_view=20 where sv.data() is the end of the referenced string, which avoids the need= =20 to special-case the end of the last token. Peter --=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/. ------=_Part_1283_28188992.1388258872556 Content-Type: text/html; charset=windows-1252 Content-Transfer-Encoding: quoted-printable


On Saturday, December 28, 2013 1:21:12 PM UTC-6, P= eter Bigot wrote:

On Friday, December 27, 2013 11:01:34 PM UTC-6, Marshall wrote:
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 th= at doesn=92t tell you anything useful).

My= understanding (which I'd like confirmed) is that sv.data() is still useful= as it provides a valid position within the referenced object, which might = be referenced by other string_view instances or in its native form.

= Thus, for example, a function object conforming to the delimiters interface= documented at http://= www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3593.html#delim= iters might return a zero-length string to denote a zero-length delimit= er (e.g., the position following a period in an English sentence).  In= this case it is the value of sv.data() that tells the caller where the del= imited sequence ends and the next sequence begins.


Sorry; I misread the details of that proposal: it explicit= ly uses an empty delimiter to indicate "not found" (too bad; zero-length de= limiters would be useful).  It does, though, specify "not found" as an= empty string_view where sv.data() is the end of the referenced string, whi= ch avoids the need to special-case the end of the last token.

Pete= r

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