220 2823 <7ebf708e-87f3-4e68-9921-c80f862c63a4@isocpp.org> article Path: news.gmane.org!not-for-mail From: Nikolay Ivchenkov Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Improvements for string literals Date: Wed, 13 Feb 2013 14:40:35 -0800 (PST) Lines: 143 Approved: news@gmane.org Message-ID: <7ebf708e-87f3-4e68-9921-c80f862c63a4@isocpp.org> References: <913f9603-aff2-4abf-a330-d4d0f8a2d1e0@isocpp.org> <5a76aa73-1940-4247-b40d-c7c1ba972246@isocpp.org> <41bc2377-7654-43f4-83f1-133edeca18d3@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_107_12740275.1360795235897" X-Trace: ger.gmane.org 1360795638 2815 80.91.229.3 (13 Feb 2013 22:47:18 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 13 Feb 2013 22:47:18 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDJK3XNWR4LRB5VP6CEAKGQEQDLAHSI@isocpp.org Wed Feb 13 23:47:40 2013 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-qa0-f69.google.com ([209.85.216.69]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1U5l74-0006Bw-HQ for gclcip-std-proposals@m.gmane.org; Wed, 13 Feb 2013 23:47:38 +0100 Original-Received: by mail-qa0-f69.google.com with SMTP id hy16sf2444546qab.8 for ; Wed, 13 Feb 2013 14:47:18 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=x-received:x-beenthere:x-received:date:from:to:message-id :in-reply-to:references:subject:mime-version:x-original-sender :reply-to:precedence:mailing-list:list-id:x-google-group-id :list-post:list-help:list-archive:list-subscribe:list-unsubscribe :content-type; bh=nnKKpR5eHhS2X+zYoUCSuE+MlRTUi/ZlflpnJevwTgA=; b=PB7Hgluhhalgq3A3iNLZzbPG9dQkGmpVoEmMy5nyb9YSR6FCBY9i8qghO+NHrTmQj9 hHbL43TPwCftvGNh5hceYcBQ+SkgEIN0XN/LKxpDvaRUorBouKVD9MoCukVta41+uu3z fn45fB8IC22SeTtuomFjsW3B3r/jc0UUTKbOwVJnxtQ4z9y2OccyB36RoWgyU+WWZdSu XXHFiZ1UQhnw24vvSXyY2bcbuQe7gbW1RBi4JYGceOZlu0PFfT/WtP11KyQYZJj2wI7L YCBlK8pFMFA6rcFGteNY12TMD7qzLI8pZp3itLLBseexerTjGJ1doHNzmjJQN/3ptC3J u95g== X-Received: by 10.224.18.199 with SMTP id x7mr1112071qaa.1.1360795638574; Wed, 13 Feb 2013 14:47:18 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.49.131.66 with SMTP id ok2ls475436qeb.79.gmail; Wed, 13 Feb 2013 14:47:11 -0800 (PST) X-Received: by 10.49.127.198 with SMTP id ni6mr1520076qeb.23.1360795236650; Wed, 13 Feb 2013 14:40:36 -0800 (PST) In-Reply-To: <41bc2377-7654-43f4-83f1-133edeca18d3@isocpp.org> X-Original-Sender: mk.ivchenkov@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:2823 Archived-At: ------=_Part_107_12740275.1360795235897 Content-Type: text/plain; charset=ISO-8859-1 On Monday, February 11, 2013 3:01:41 PM UTC+4, Nicol Bolas wrote: > > It would be possible to improve classes for immutable strings if >> parameters could be declared with 'static constexpr' and the overload >> resolution could select appropriate function depending on whether the >> argument is known to be a constexpr object with static storage duration: >> >> template >> class basic_immutable_string >> { >> public: >> template >> basic_immutable_string(static constexpr CharT (&s)[N]); // #1 >> basic_immutable_string(CharT const *s); // #2 >> .... >> }; >> >> using immutable_string = basic_immutable_string; >> >> template >> void f(static constexpr char (&x)[N]) >> { >> static constexpr char a1[] = "text"; >> static char a2[] = "text"; >> auto &ra1 = a1; >> >> immutable_string s0 = x; // calls #1 >> immutable_string s1 = a1; // calls #1 >> immutable_string s2 = a2; // calls #2 >> immutable_string s3 = ra1; // calls #2 >> immutable_string s4 = "text"; // calls #1 >> } >> >> > Not quite: > > static constexpr char ar3[] = {'n', 'o', 't', ' ', 'l', 'i', 't', 'e', 'r' > , 'a', 'l'}; > > That would work just as well with your way. > If we remove the constexpr specifier, then initialization immutable_string s = ar3; will not be well-defined, because ar3 is not a null-terminated string. In the presence of constexpr the effect of such initialization could be considered as undefined similarly. -- --- 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/?hl=en. ------=_Part_107_12740275.1360795235897 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable On Monday, February 11, 2013 3:01:41 PM UTC+4, Nicol Bolas wrote:
It would be possible to improve classes for immutable strings if para= meters could be declared with 'static constexpr' and the overload resolutio= n could select appropriate function depending on whether the argument is kn= own to be a constexpr object with static storage duration:

 &nb= sp;  template <class CharT>
     &nb= sp;  class basic_immutable_string
    {
 &nb= sp;  public:
        template &l= t;std::size_t N>
        &nbs= p;   basic_immutable_string(static constexpr CharT (&s)[N]); = // #1
        basic_immutable_string(= CharT const *s); // #2
        ....    };

    using immutable_string = =3D basic_immutable_string<char>;

    template = <std::size_t N>
        void f(= static constexpr char (&x)[N])
    {
  &= nbsp;     static constexpr char a1[] =3D "text";
&nb= sp;       static char a2[] =3D "text";
&nb= sp;       auto &ra1 =3D a1;

 =        immutable_string s0 =3D x; // calls #1=
        immutable_string s1 =3D a1; = // calls #1
        immutable_string = s2 =3D a2; // calls #2
        immuta= ble_string s3 =3D ra1; // calls #2
      &= nbsp; immutable_string s4 =3D "text"; // calls #1
    }


Not quite:

static constexpr char ar3[] =3D {'n', 'o'= , 't',<= span style=3D"color:#000"> ' ', 'l', 'i', 't', 'e', 'r'= , 'a',<= span style=3D"color:#000"> 'l'};

That would work just as well with your way.

If we remove the constexpr specifier, then initialization=

    immutable_string s =3D ar3;

will not be w= ell-defined, because ar3 is not a null-terminated string. In the presence o= f constexpr the effect of such initialization could be considered as undefi= ned similarly.

--
 
---
You received this message because you are subscribed to the Google Groups &= quot;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-pro= posals/?hl=3Den.
 
 
------=_Part_107_12740275.1360795235897-- .