220 29478 <35fe3945-71cf-4958-8f92-59df0ef98fae@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: inkwizytoryankes@gmail.com Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Allowing string literals to match `char...` packs in templates Date: Fri, 18 Nov 2016 12:47:32 -0800 (PST) Lines: 90 Approved: news@gmane.org Message-ID: <35fe3945-71cf-4958-8f92-59df0ef98fae@isocpp.org> References: <9de07b5f-f870-4a02-882f-54f9fdd12ffd@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_6446_1737430314.1479502052265" X-Trace: blaine.gmane.org 1479502059 30914 195.159.176.226 (18 Nov 2016 20:47:39 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Fri, 18 Nov 2016 20:47:39 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBDDLTAGNTIBBBZGRXXAQKGQENL64GQY@isocpp.org Fri Nov 18 21:47:34 2016 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-pg0-f71.google.com ([74.125.83.71]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1c7q4I-0006IE-DA for gclcip-std-proposals@m.gmane.org; Fri, 18 Nov 2016 21:47:30 +0100 Original-Received: by mail-pg0-f71.google.com with SMTP id p66sf272618417pga.4 for ; Fri, 18 Nov 2016 12:47:34 -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=rzrSK7/Bf4ZHagJ5TIXrED3XHRJnZdMk/pD1jeXCUrM=; b=VciSED7F9Y7yLAtv7sNhjCyiy2rw9k6qg72vWa9j7rVGAtVEUbfXkaFYBbs7RsuKyN w2G/ZVwvzfU6cgeSv5NijKwaeokYLDVCt+NcEE+GT3iMdLsyaJfsN8GruSkaXqsnUuMw 1IX8P4mp0fksWyZPNkzkeDky0C/rElFtNLVfKqFp21gAlyly8uXlvpwhB/4ErYWmmQ1Y fOFvpqyYEU+sc5n7rO357q+yYPZXbHbHm8kt73Tjd8OtfDKhVf4snKKPkEMPcGOsSmoz g7QOswaFpeZB/pTKV3YoNgk4uKvdQRfpA0XrCsTtJjN3Mmx0imNZ3COEcvEatTzZUt55 ytjg== 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=rzrSK7/Bf4ZHagJ5TIXrED3XHRJnZdMk/pD1jeXCUrM=; b=FHdOFJjrPUmFJ6dH83F0uBkzwuXnemuDmw2daoCIjG21GkRxwL9PCF/4KkJLfeN0x6 o1SZ4k29JRoXMgW6zg26rcsxS999TvFuhxr7VnpxtBgrm7QngJpp+LsZin6AcbnbgK3g gKFMNwYvO3jpb9ZLj+dElO6HJJSh0wMFZ1eIo/jGA6sAIE/umIU7HysdxujZC0pBo1rE Qwv1eBfenEhP42+N76T1+P6/w7mYbhufZqf2DdwUPHaIdzTESpJDHZyNc8lHCwRFDp2v 0TVE0/Mm4AVDlG4jhsNUfOyNNBqG9mpeqzTKxZUjT17yd8Xd6pr5kJeH+u2RnvVHp9lL 3yrw== 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=rzrSK7/Bf4ZHagJ5TIXrED3XHRJnZdMk/pD1jeXCUrM=; b=YGrfToFP+Zaiqn/0BB2XxoJbxm1r6gz4it1glSGHb+bY+ARo7Z3NKbbNrvk85TmiaH qK8WLH1GKsA++soqrgVL1mhSrNARkQ4v1z+vAsUClniNW1pD+fMsvqvqzetHWUnCgVNb 7fxHi+Ltc0SPY4gMczXckm+r2BGzEMVF3ybIBNp6Po/F8mY++pOSIcvp6Dz8iB0szJe3 jnCfVuO7gHW8KvSvxpkUgQMSIxJNtDGEZ1b0TiV6QHTO5fNlmmD+Jl6HtOYVaLyCrOXY fP7hJdmsuWutONHJGzMovGUj1Lm+ATaW3PqG19+PnexFuAVUV+iPOyrbTZOuR8aOmSIS 6+Bw== X-Gm-Message-State: AKaTC028cz+RjTyFpvFfVVGrw6MvKWzelfGaIklvVbwiITSDzAQ+iYXp+unBXEYi3FKDQw== X-Received: by 10.99.64.194 with SMTP id n185mr615362pga.53.1479502053499; Fri, 18 Nov 2016 12:47:33 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.157.46.13 with SMTP id q13ls7554271otb.20.gmail; Fri, 18 Nov 2016 12:47:32 -0800 (PST) X-Received: by 10.157.11.248 with SMTP id 111mr246611oth.4.1479502052690; Fri, 18 Nov 2016 12:47:32 -0800 (PST) In-Reply-To: X-Original-Sender: inkwizytoryankes@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:29478 Archived-At: ------=_Part_6446_1737430314.1479502052265 Content-Type: multipart/alternative; boundary="----=_Part_6447_813059815.1479502052265" ------=_Part_6447_813059815.1479502052265 Content-Type: text/plain; charset=UTF-8 On Thursday, November 17, 2016 at 6:28:26 AM UTC+1, Louis Dionne wrote: > > Let me just expand a bit on what Matt said. > > I think this is a brilliant idea, but I don't think it's going to work, > for the same reason > as my P0424R0 paper was not warmly received. The reason is that > implementers > don't want anything that encourages the use of large template parameter > lists, > because the representation of that inside the compiler is too inefficient. > They don't > want a single template parameter per character in the string, because the > structure > that represents a template parameter in the compiler is expensive. > Instead, they'd > rather have a single structure that represents all the characters. I'm not > sure why they > can't just represent a character pack in a more efficient manner, but > that's what I > was told when I presented in EWG. > > Fact that storing string in template parameters list is ineffective did not stop GCC and Clang from implementing this: https://godbolt.org/g/VjJzJi https://godbolt.org/g/1DVftM Thanks to that we can test how far we need push compilers to break when we use this UDL. -- 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. To view this discussion on the web visit https://groups.google.com/a/isocpp.org/d/msgid/std-proposals/35fe3945-71cf-4958-8f92-59df0ef98fae%40isocpp.org. ------=_Part_6447_813059815.1479502052265 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable


On Thursday, November 17, 2016 at 6:28:26 AM UTC+1= , Louis Dionne wrote:
Let me just expand a bit on what Matt said.

I think this is a brilliant idea, but I don't think it's go= ing to work, for the same reason
as my P0424R0 paper was not warm= ly received. The reason is that implementers
don't want anyth= ing that encourages the use of large template parameter lists,
be= cause the representation of that inside the compiler is too inefficient. Th= ey don't
want a single template parameter per character in th= e string, because the structure
that represents a template parame= ter in the compiler is expensive. Instead, they'd
rather have= a single structure that represents all the characters. I'm not sure wh= y they
can't just represent a character pack in a more effici= ent manner, but that's what I
was told when I presented in EW= G.


Fact that storing string in templat= e parameters list is ineffective did not stop GCC and Clang from implementi= ng this:
https://godbolt.org/g/VjJzJi
https://godbolt.org/g/1DVftMThanks to that we can test how far we need push compilers to break when we= use this UDL.

--
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-proposa= ls+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/35fe3945-71cf-4958-8f92-59df0ef98fae= %40isocpp.org.
------=_Part_6447_813059815.1479502052265-- ------=_Part_6446_1737430314.1479502052265-- .