220 29434 <10914b55-c188-4573-a4c7-ba686f213a38@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: TONGARI J Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Allowing string literals to match `char...` packs in templates Date: Wed, 16 Nov 2016 23:40:24 -0800 (PST) Lines: 107 Approved: news@gmane.org Message-ID: <10914b55-c188-4573-a4c7-ba686f213a38@isocpp.org> References: <9de07b5f-f870-4a02-882f-54f9fdd12ffd@isocpp.org> <6b73bf50-4189-4d5d-a2c0-2debb085659e@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_5649_555192666.1479368424159" X-Trace: blaine.gmane.org 1479368426 17839 195.159.176.226 (17 Nov 2016 07:40:26 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Thu, 17 Nov 2016 07:40:26 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCC3NA775MLBB2F5WXAQKGQE5TE7WMQ@isocpp.org Thu Nov 17 08:40:22 2016 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-pf0-f198.google.com ([209.85.192.198]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1c7HJ0-0003W2-AY for gclcip-std-proposals@m.gmane.org; Thu, 17 Nov 2016 08:40:22 +0100 Original-Received: by mail-pf0-f198.google.com with SMTP id 144sf105861971pfv.5 for ; Wed, 16 Nov 2016 23:40:25 -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=zPQojh1XNTMABffU6Ma2CtPObiOa3u7P4kdUu1VKpYc=; b=lUIeKGRIT3rHNHXEgQSpPNZ8cWF152qGtWDemIpO/OeMRbty2/zcFZim0l3563AWIK +OU1sl443cFnzCkO4BXHACMr/lhhNjoVyoPB3/OMoRl0ddPQbu3xu8PT1mAWzmeLYEk2 f3bxqv74jWiKzfXpOss8wtSAAqPzG8ANjx6obsb86vVUCMQqAywMT1Rj2VdB9yGwSSlh SApdCTz/XzqyFbhZguJSVzETIwny2a5tzklL2g65UdFkoa8flP+udy9grOpt3Qniaxcy kjpzE+u7X3Z7JmZ3j88TadPzFY1rT0i1k5wfFAtNxpCjbvw8OviP2lXCq2T8QDCJqnoS kSaA== 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=zPQojh1XNTMABffU6Ma2CtPObiOa3u7P4kdUu1VKpYc=; b=QcIfVvLdfJMjeR10+hJ5Dby5LuyMrk7++wyEHY1F20Yr0XN3bl23GA9xEjVfWLVgBa ks4/lxcKkAugjsmoH1KndjqZwzwEKizT+2nydIvNxU1IFGS3H/1JSw7sPdcCjzN7Kxop xRquiZ3qa0SaeriIkaauyH71i9AJmYLVoZn6iE+Ug7jwwR5gUpbSaXV/7btCg/G/8Iao VZtRQHDDP/tsn9uYZvyLVMIdcqCCx0j5O6JUwGjIukHjpZ4U4tiaa/mTIVmaczcqwbWF K6vAu915g+spvBLHZxqKn3yil1Prl90dfBkZWshYy+cOVp7HjVhuzNpf9Q9bB8oWDHYH gU7A== 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=zPQojh1XNTMABffU6Ma2CtPObiOa3u7P4kdUu1VKpYc=; b=c8zWHRvx9fmfcef0yfaCtCKoTq0iwkXzcVyc6zrf5Js7XKIwQMLIaUg0gQXGyxStxQ Xw3XgYFQnX2knUM/mwU64+gLPDakZm9XmQAxgdk57CZfYbanqMvje1TGl4CLcfpVyQIA 65w6P5P46dGMEFfboT37j1ABrdHH2QJlOV2/i20q45ZunhJ7gc87QuevNuCenqnig6tk kXGnz/SxziVLeZF+6ifrmpxrjkDzOvmBgFRqLjbgiJIxaKipDZ8sIGTVXbrVwfShNIn/ fNWdrvOMCQHvajM050Wby8aevvF8PDOgsc5gkFKXRdOSeoHV4IyGlluSSWs8ktcVnEKM ejpw== X-Gm-Message-State: ABUngvcQJoS3xKY3OP2hgCyQkBxi9NASa8q6acBcZW1EioyOtaEZ74HW5N+Q9MDWlucQvQ== X-Received: by 10.99.127.83 with SMTP id p19mr637785pgn.107.1479368425350; Wed, 16 Nov 2016 23:40:25 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.157.36.65 with SMTP id p59ls3491421ota.40.gmail; Wed, 16 Nov 2016 23:40:24 -0800 (PST) X-Received: by 10.157.20.197 with SMTP id r5mr101992otr.9.1479368424591; Wed, 16 Nov 2016 23:40:24 -0800 (PST) In-Reply-To: X-Original-Sender: tongari95@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:29434 Archived-At: ------=_Part_5649_555192666.1479368424159 Content-Type: multipart/alternative; boundary="----=_Part_5650_413995084.1479368424160" ------=_Part_5650_413995084.1479368424160 Content-Type: text/plain; charset=UTF-8 On Thursday, November 17, 2016 at 3:23:00 PM UTC+8, Louis Dionne wrote: > > No, this has not been discussed AFAICT. That's not a bad idea, but it does > seem very magic to me. > I don't know whether it's more desirable to introduce this special case or > to "fix" the problem by > allowing user defined types with some restrictions as template arguments. > Certainly the latter is > cleaner, but also much more difficult. > It's only as magic as lambda expressions :) The idea is very similar, the big difference is that lambda will give you different types even if the expressions are lexically the same, while this will give you the same type as long as the string-literals are the same. Further more, we can define some useful operations to help string processing, e.g. static_assert(is_same::value); This is certainly not as general as allowing UDTs as template arguments, but should solve a practical problem in compile-time string processing. -- You received this message because you are subscribed to the Google Groups "ISO C++ Standard - Future Proposals" group. 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On Thursday, November 17, 2016 at 3:23:00 PM UTC+8, Louis = Dionne wrote:
= No, this has not been discussed AFAICT. That's not a bad idea, but it d= oes seem very magic to me.
I don't know whether it's more desir= able to introduce this special case or to "fix" the problem by
allowing user defined types with some restrictions as template argu= ments. Certainly the latter is
cleaner, but also much more diffic= ult.

It's only as magic as lambda expressi= ons :)
Furthe= r more, we can define some useful operations to help string processing, e.g= ..
stati= c_assert(<= /span>is_same<decltype("Hello"lit + " World"lit), decltype("Hello World"lit)>::value);

This is certainly not as general as allowing UDTs a= s template arguments, but should solve a practical problem in compile-time = string processing.

--
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