220 8480 <52CE0F54.5020800@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: Thu, 09 Jan 2014 10:54:12 +0800 Lines: 44 Approved: news@gmane.org Message-ID: <52CE0F54.5020800@gmail.com> References: <-5123564187529511709@gmail297201516> <52CB7506.1000906@gmail.com> <62bda680-3dd7-4be8-8ac5-0d2e08bf6d99@isocpp.org> <52CDFB2D.4050703@gmail.com> <-9126987679220332623@gmail297201516> 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 Content-Transfer-Encoding: quoted-printable X-Trace: ger.gmane.org 1389236054 5642 80.91.229.3 (9 Jan 2014 02:54:14 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Thu, 9 Jan 2014 02:54:14 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCW25A7E3QCRBWU6XCLAKGQENF3XIHI@isocpp.org Thu Jan 09 03:54:20 2014 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-pd0-f198.google.com ([209.85.192.198]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1W15lE-0001ii-4g for gclcip-std-proposals@m.gmane.org; Thu, 09 Jan 2014 03:54:20 +0100 Original-Received: by mail-pd0-f198.google.com with SMTP id g10sf6049829pdj.5 for ; Wed, 08 Jan 2014 18:54:19 -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:content-transfer-encoding; bh=v1XZa6dEL8ahFb5QZwNDOdiUpAsVFqDdKj9WWDn5KmI=; b=aO5tHiQ4FsCzeer7r0H0LPn+csuZQYGbKMLy/E5ZSeI/gZh64Ax5yX7a7aySeq3Jk/ lbjKAQlPi9487blTb3En8uUSwgyxyds2aAtGkjiHBku0SdINoMSviWUKEsStEwS8cCgv HzVeOTS5oJCNRgT0esFeiigplAQk7Pfj8m88NzWRj31INm77V1yw4hRq/Zdt2AYODU6/ +y86+TXf4qWjB84YbYUklcZDIL+B4wUXBuIug2RQjnlpYighzvambsNUfSYa+EitBqbX WTeKOCyddobongF4t+n5VdTjsteYmUudEOKDQtKh63iz1R69aa0APf9Es3s7Bdts54+L qQ7 X-Gm-Message-State: ALoCoQnpYxL669CkrXaLdBV0+z8Qws3KLr6ySj/DCkGD78Zo0TTprR3gTVZeNAf9H09Bo9JOnBea X-Received: by 10.66.66.35 with SMTP id c3mr283354pat.12.1389236058979; Wed, 08 Jan 2014 18:54:18 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.49.95.229 with SMTP id dn5ls832359qeb.48.gmail; Wed, 08 Jan 2014 18:54:18 -0800 (PST) X-Received: by 10.236.62.194 with SMTP id y42mr889014yhc.54.1389236058122; Wed, 08 Jan 2014 18:54:18 -0800 (PST) Original-Received: from mail-oa0-x231.google.com (mail-oa0-x231.google.com [2607:f8b0:4003:c02::231]) by mx.google.com with ESMTPS id g70si2522432yhd.243.2014.01.08.18.54.18 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 08 Jan 2014 18:54:18 -0800 (PST) Received-SPF: pass (google.com: domain of potswa@gmail.com designates 2607:f8b0:4003:c02::231 as permitted sender) client-ip=2607:f8b0:4003:c02::231; Original-Received: by mail-oa0-f49.google.com with SMTP id n16so2750201oag.22 for ; Wed, 08 Jan 2014 18:54:17 -0800 (PST) X-Received: by 10.182.60.233 with SMTP id k9mr474489obr.34.1389236057737; Wed, 08 Jan 2014 18:54:17 -0800 (PST) Original-Received: from Davids-MacBook-Pro.local ([121.54.54.58]) by mx.google.com with ESMTPSA id ii8sm3560677obb.11.2014.01.08.18.54.15 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 08 Jan 2014 18:54:16 -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: <-9126987679220332623@gmail297201516> X-Original-Sender: potswa@gmail.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of potswa@gmail.com designates 2607:f8b0:4003:c02::231 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:8480 Archived-At: On 1/9/14 10:41 AM, Richard Smith wrote: > On Wed Jan 08 2014 at 5:28:21 PM, David Krauss wrote: > > It's not an overload, it's a partial specialization. OK, that wasn't clear from the example. So do you intend that an=20 identifier declared with "?" never be used? What could you possibly do=20 with X? Quoting the previous message: >> I still don't see the value of an identifier, as opposed to a pack >> expansion element, that can be either a type or a value. And such a name >> would throw a wrench into template parsing. They could *only* be used as >> explicit template arguments to functions as in my example above, or to >> template template parameters with "?"-like parameter lists. Edit: You couldn't even use X in these cases, because parse time=20 ambiguity of a template argument is always resolved in favor of a=20 typename ([temp.arg] =A714.3/2). >> If you end up needing to use is_type, you're already in deep shit. >> >> On the other hand, parameter lists are already unpacked using >> overloading, or partial specialization which works the same way. This >> gives you a branching point to different code paths for type, value, or >> template, which can already be written and parsed without redesigning >> dependent name lookup. >> >> This is why I think "..." is sufficient with no motivation for "?" or >> any provision for a single argument. >> --=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. Visit this group at http://groups.google.com/a/isocpp.org/group/std-proposa= ls/. .