220 29438 article Path: news.gmane.org!.POSTED!not-for-mail From: Louis Dionne Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Allowing string literals to match `char...` packs in templates Date: Thu, 17 Nov 2016 00:23:19 -0800 (PST) Lines: 113 Approved: news@gmane.org Message-ID: References: <9de07b5f-f870-4a02-882f-54f9fdd12ffd@isocpp.org> <6b73bf50-4189-4d5d-a2c0-2debb085659e@isocpp.org> <10914b55-c188-4573-a4c7-ba686f213a38@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_4940_1827998296.1479370999176" X-Trace: blaine.gmane.org 1479371003 10252 195.159.176.226 (17 Nov 2016 08:23:23 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Thu, 17 Nov 2016 08:23:23 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCV3HSWWRMMRB56RWXAQKGQE7F6KI4A@isocpp.org Thu Nov 17 09:23:18 2016 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-vk0-f70.google.com ([209.85.213.70]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1c7HyX-0001X2-Hm for gclcip-std-proposals@m.gmane.org; Thu, 17 Nov 2016 09:23:17 +0100 Original-Received: by mail-vk0-f70.google.com with SMTP id 19sf132411939vko.0 for ; Thu, 17 Nov 2016 00:23:21 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:message-id:in-reply-to:references:subject:mime-version :x-original-sender:reply-to:precedence:mailing-list:list-id :x-spam-checked-in-group:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=LcFNCoOn5gcJ/dDXihlQrNcuAq2iIbd/+o1k29uSqOI=; b=wUHA793ZAyr2ZdekijL1LU3UTAIXRk+DIVi4SXwDAbAn78rPxCUU4VBncXIJcN1nox vDQcx7UDHg1ITtJQ3nQVatnZQ0kfuIj5AhTPM3MN3Vh88Rlz/A6YZzQ+OwLGJkOs83UR F3bfV5gOIe7qRfqX+TsN5/iyQQOvRCfavJurBKc2ShXAe/LSB4qxkYHoH2BOOLhZHKC6 KsgbkdxRkPex1oQuGd+UJY6xGbsuXI/hHicoCvlm13NJmZnj6erZ1/5QZc2knHG0T50I JFEHi+Y6MiStZYPzJTFRuQYkiJpP7PdoWa6+D9WORS9aUBwFUIByaem4m93MaZ2uYFZ9 4YZQ== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=date:from:to:message-id:in-reply-to:references:subject:mime-version :x-original-sender:reply-to:precedence:mailing-list:list-id :x-spam-checked-in-group:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=LcFNCoOn5gcJ/dDXihlQrNcuAq2iIbd/+o1k29uSqOI=; b=VuqV7iJY5GBBnqwIgzix1j68Habqf9N1iOB7LFKQvt/i/hnTetQyOdSq7JDIILPjc8 uA6wQ2sn7rU5fF3Oh7MaW6EglIBjPhBWE5Q7+bqRbhr2hHzwuBv3jVyjp854pqimTQrZ UTedqLzhbYto9k0QnIoF+MZ2hLYZdfWAq3gwk/xue6LAEo/DCFCodNfi4WcRV0rN5iXW 1Eo6NV51tBXAqRJhDqdX1ZK0rBiES75KH+A8KPhdL9Zf/FaCphYrwxGd7VjUZD+WpsyT 0qBxcHSx7fmopvFrm0N/PKztoXqSIQ1p7/TXXTKHAxpZG0ON/AX/mh5LMr6GoqZhT/AC Zk7w== 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:x-spam-checked-in-group:list-post:list-help :list-archive:list-subscribe:list-unsubscribe; bh=LcFNCoOn5gcJ/dDXihlQrNcuAq2iIbd/+o1k29uSqOI=; b=FQInNEl3NF4UeSYa9IZrGJRO1MStL7nzpEsBmlqJfoluF9ndJRxN1cOg++USIdAv3U hnJkAJDYt+x/ylh0JIiNIb8YCzjh1O6TiuqN6IftnE0xcc5H2ntpSJXRuYT5wwPArWhI VxRxdKg0dq+cscwoSTjPFnyufffxiQQhzzn8uE8+iCrSr8YK0VWENV0/wsDxGw4EaTx/ eNUoV5+5x1QhW8lzEz8nEwQrN2L0eVY1sH4Dcy/PJ+jE+3mthZS6XTf/8qvuLSvPjwTd O/RJ+RM6gz5dopc+WS+lnUZiJqpRN/t8FAR40bUxklJtr4MGDty9rXR0AwOPlpPhe9aY yoAA== X-Gm-Message-State: AKaTC02xG0H+7neCblJ9RyJBQUwBtQzGOlOTieciIJ65h2Qnmyd6O7DSyzgaysIgiCnyCw== X-Received: by 10.159.35.118 with SMTP id 109mr381520uae.13.1479371000406; Thu, 17 Nov 2016 00:23:20 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.157.56.209 with SMTP id k17ls3639612ote.14.gmail; Thu, 17 Nov 2016 00:23:19 -0800 (PST) X-Received: by 10.157.37.125 with SMTP id j58mr114524otd.18.1479370999620; Thu, 17 Nov 2016 00:23:19 -0800 (PST) In-Reply-To: X-Original-Sender: ldionne.2@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:29438 Archived-At: ------=_Part_4940_1827998296.1479370999176 Content-Type: multipart/alternative; boundary="----=_Part_4941_694291348.1479370999177" ------=_Part_4941_694291348.1479370999177 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Another problem is that "different" literals for address purposes could be= =20 the same when doing a strcmp-style comparison. Consider: foo<"hello world"> foo<"hello world\0abcd"> Should these two resolve to the same template? If we use the address of=20 literals, certainly not. If we compare the contents of the string, I guess that=20 remains an open issue but the two behaviors could be envisioned. Louis On Thursday, 17 November 2016 09:19:32 UTC+1, Ville Voutilainen wrote: > > On 17 November 2016 at 10:13, Jonathan M=C3=BCller=20 > > wrote:=20 > > Sorry if I'm asking the obvious question here: Why not guarantee that= =20 > > different string literals have different addresses and the same string= =20 > > literal has the same address and use const char* as non-type template= =20 > > parameters?=20 > > It's less of a problem of guaranteeing that different literals have=20 > different addresses, and=20 > more a problem of avoiding identical literals possibly having=20 > different addresses. Therefore=20 > it's better to have the template equivalence be determined by the=20 > contents of the string=20 > rather than the address.=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. To view this discussion on the web visit https://groups.google.com/a/isocpp= ..org/d/msgid/std-proposals/f8c8b5e6-3d69-4605-bd5d-161c3e47ca7e%40isocpp.or= g. ------=_Part_4941_694291348.1479370999177 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
Another problem is that "different" li= terals for address purposes could be the
same when doing a strcmp= -style comparison. Consider:

=C2=A0 =C2=A0 foo<= "hello world">
=C2=A0 =C2=A0 foo<"hello worl= d\0abcd">

Should these two resolve to the = same template? If we use the address of literals,
certainly not. = If we compare the contents of the string, I guess that remains an
open issue but the two behaviors could be envisioned.

=
Louis


On Thursday, 17 November 2016 09:19:32 UTC+1,= Ville Voutilainen wrote:
On 1= 7 November 2016 at 10:13, Jonathan M=C3=BCller
<jonathanm...@gmail.com> wrote:
> Sorry if I'm asking the obvious question here: Why not guarant= ee that
> different string literals have different addresses and the same st= ring
> literal has the same address and use const char* as non-type templ= ate
> parameters?

It's less of a problem of guaranteeing that different literals have
different addresses, and
more a problem of avoiding identical literals possibly having
different addresses. Therefore
it's better to have the template equivalence be determined by the
contents of the string
rather than the address.

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To unsubscribe from this group and stop receiving emails from it, send an e= mail to std-proposa= ls+unsubscribe@isocpp.org.
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To view this discussion on the web visit https://groups.google.= com/a/isocpp.org/d/msgid/std-proposals/f8c8b5e6-3d69-4605-bd5d-161c3e47ca7e= %40isocpp.org.
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