220 8497 <52CF3D80.9090702@gmail.com> article Path: news.gmane.org!not-for-mail From: David Krauss Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: A new keyword for either a type or a variable (typical use case for variadic template template)? Date: Fri, 10 Jan 2014 08:23:28 +0800 Lines: 35 Approved: news@gmane.org Message-ID: <52CF3D80.9090702@gmail.com> References: <-5123564187529511709@gmail297201516> <52CB7506.1000906@gmail.com> <62bda680-3dd7-4be8-8ac5-0d2e08bf6d99@isocpp.org> <52CDFB2D.4050703@gmail.com> <-9126987679220332623@gmail297201516> <52CE0F54.5020800@gmail.com> <52CF3AB0.7090102@gmail.com> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed X-Trace: ger.gmane.org 1389313471 17638 80.91.229.3 (10 Jan 2014 00:24:31 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Fri, 10 Jan 2014 00:24:31 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCW25A7E3QCRBQX3XSLAKGQE72XDRLY@isocpp.org Fri Jan 10 01:24:38 2014 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-pb0-f72.google.com ([209.85.160.72]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1W1Pts-0000a2-D5 for gclcip-std-proposals@m.gmane.org; Fri, 10 Jan 2014 01:24:36 +0100 Original-Received: by mail-pb0-f72.google.com with SMTP id jt11sf8742711pbb.7 for ; Thu, 09 Jan 2014 16:24:35 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:message-id:date:from:user-agent:mime-version:to :subject:references:in-reply-to:x-original-sender :x-original-authentication-results:reply-to:precedence:mailing-list :list-id:list-post:list-help:list-archive:list-subscribe :list-unsubscribe:content-type; bh=NKNC8rjRXWHQKWSbJdd31qlIjNrNhR7Z1mDNhZtGSuI=; b=XWcXMkXch70jCRY8a0AGK8lmbC4nzG8gS1cx4n+x5LPfifLNaeWtSuGUA3COTP/WX4 k8YRhxEioMUqxXfLd+rKJMRt2XY9iIO6DtqtFpYFSgYlHmTVaSV1CUX9JNa71dbbzTEJ LfNt7vx7kw/Z/xp7EEhEdWj/5mnfxbu5gFPk9LFZQvw0Chd6nEbRZ7hceFtezJGu59r8 j41ONLtBstpCHrY/kBeV43Rioy8zsziIyhWoy7saNur/KIJKWhquD3cXUTDiyZkM4a0/ gMX4S7wOVJVnKX2DzPEnd/w9yHMd2mnWAWhMtM81qyOPrStqGJRt6sZgVS3JC0gXm3vf mO4Q== X-Gm-Message-State: ALoCoQmzjsGvfkuH1cUNRj9KsVClWZjZeSRIbbalmR3q6fiWvCvoetRcl29ieJVnu7eYvgHAUaLv X-Received: by 10.66.240.4 with SMTP id vw4mr2345116pac.10.1389313475235; Thu, 09 Jan 2014 16:24:35 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.49.40.164 with SMTP id y4ls1400978qek.89.gmail; Thu, 09 Jan 2014 16:24:34 -0800 (PST) X-Received: by 10.236.122.165 with SMTP id t25mr8107181yhh.46.1389313474229; Thu, 09 Jan 2014 16:24:34 -0800 (PST) Original-Received: from mail-pb0-x22a.google.com (mail-pb0-x22a.google.com [2607:f8b0:400e:c01::22a]) by mx.google.com with ESMTPS id s23si6707462yhf.103.2014.01.09.16.24.34 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Thu, 09 Jan 2014 16:24:34 -0800 (PST) Received-SPF: pass (google.com: domain of potswa@gmail.com designates 2607:f8b0:400e:c01::22a as permitted sender) client-ip=2607:f8b0:400e:c01::22a; Original-Received: by mail-pb0-f42.google.com with SMTP id uo5so3731541pbc.1 for ; Thu, 09 Jan 2014 16:24:33 -0800 (PST) X-Received: by 10.68.134.98 with SMTP id pj2mr7094026pbb.110.1389313473370; Thu, 09 Jan 2014 16:24:33 -0800 (PST) Original-Received: from Davids-MacBook-Pro.local ([121.54.44.159]) by mx.google.com with ESMTPSA id yd4sm12767057pbc.13.2014.01.09.16.23.49 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Thu, 09 Jan 2014 16:24:32 -0800 (PST) User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.8; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 In-Reply-To: <52CF3AB0.7090102@gmail.com> X-Original-Sender: potswa@gmail.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of potswa@gmail.com designates 2607:f8b0:400e:c01::22a as permitted sender) smtp.mail=potswa@gmail.com; dkim=pass header.i=@gmail.com; dmarc=pass (p=NONE dis=NONE) header.from=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:8497 Archived-At: On 1/10/14 8:11 AM, David Krauss wrote: > On 1/9/14 11:18 AM, Richard Smith wrote: >> The useful thing about introducing a new feature is that you get to >> specify >> how it works =) Naturally, we would specify that passing a generic >> template >> argument to another template preserves the kind of template argument. > > But how can you make that work without redoing how parsers must > classify type-dependent expressions? And what's the benefit, given > that overloading/partial specialization already solve the problem? I should be more specific. Given "?", you can peel off a fully-generic argument from a pack, and pass it to another template. But the other template must be either fully-generic, or overloaded/partially specialized. So you might as well peel the pack in the target overloaded/partially specialized template. All "?" buys you is the freedom to add a dispatcher between components which are actually necessary. I don't see any applications for fully-generic arguments outside metaprocessing, e.g. of packs. There is no runtime code application parameterized over all types or all values of any type. For value-like types, i.e. std::integral_constant, it is idiomatic (and makes perfect sense) to deal with runtime instances of a stateless class. -- --- You received this message because you are subscribed to the Google Groups "ISO C++ Standard - Future Proposals" group. 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