220 8143 <52AF8782.1070405@gmail.com> article Path: news.gmane.org!not-for-mail From: David Krauss Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: A compile-time string literal library type Date: Tue, 17 Dec 2013 07:06:42 +0800 Lines: 33 Approved: news@gmane.org Message-ID: <52AF8782.1070405@gmail.com> References: <52AE9F22.1070403@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 1387235204 18361 80.91.229.3 (16 Dec 2013 23:06:44 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Mon, 16 Dec 2013 23:06:44 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCW25A7E3QCRBCEPX2KQKGQECJK43LY@isocpp.org Tue Dec 17 00:06:50 2013 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-yh0-f69.google.com ([209.85.213.69]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1VshFR-0000bL-Va for gclcip-std-proposals@m.gmane.org; Tue, 17 Dec 2013 00:06:50 +0100 Original-Received: by mail-yh0-f69.google.com with SMTP id a41sf10660476yho.4 for ; Mon, 16 Dec 2013 15:06:49 -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=3ImXG35zwCMwt6zeMYvuaRxkIqI8EwwzZLAZuq7WGOE=; b=AxONvMPbQEOx/zuz0JpzUSL9Wqxq39fkwPJM0sh/ZEvbtZ/bvEu4tMtOawvbf3SW52 409lOqKCuUYJxpmRueDSYPwGlZkXQgVwDUh2v9bVfWsj9aKH0rzmWHfbr5j/d3MHfmT3 cyi0lEEL9ofzu56/hWVJ5QM9ujZ41LBOoK5UNHMPtMDZHdOt5qv4fKABPFVIsazv822Z iJUWeuP6N38+4dg4oD4BZNlIrpjKlX9M/7u+bchLzvtqpA7NLWox+vOnTbSOpM3UO4cr 7E8dbsacPo53gWHxORw38rLu2nIqQXsC8DFNT5+3SV+/m/sIFDb0QRIHp+4cy8lpECFV daGw== X-Gm-Message-State: ALoCoQn4xTCyNXn26KmV9rRUDSNg+8wbMr5EgXQ3jNSd3DAD5fkcbOnKJUCLxiOCiYrFyrmkRJr5 X-Received: by 10.52.159.99 with SMTP id xb3mr6141909vdb.4.1387235209006; Mon, 16 Dec 2013 15:06:49 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.49.3.228 with SMTP id f4ls2332699qef.85.gmail; Mon, 16 Dec 2013 15:06:48 -0800 (PST) X-Received: by 10.236.160.9 with SMTP id t9mr15079790yhk.10.1387235208187; Mon, 16 Dec 2013 15:06:48 -0800 (PST) Original-Received: from mail-pa0-x22b.google.com (mail-pa0-x22b.google.com [2607:f8b0:400e:c03::22b]) by mx.google.com with ESMTPS id j69si13885395yhb.246.2013.12.16.15.06.48 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Mon, 16 Dec 2013 15:06:48 -0800 (PST) Received-SPF: pass (google.com: domain of potswa@gmail.com designates 2607:f8b0:400e:c03::22b as permitted sender) client-ip=2607:f8b0:400e:c03::22b; Original-Received: by mail-pa0-f43.google.com with SMTP id bj1so3607734pad.2 for ; Mon, 16 Dec 2013 15:06:47 -0800 (PST) X-Received: by 10.68.29.72 with SMTP id i8mr23604484pbh.116.1387235207223; Mon, 16 Dec 2013 15:06:47 -0800 (PST) Original-Received: from Davids-MacBook-Pro.local ([121.54.54.135]) by mx.google.com with ESMTPSA id ug2sm39846627pac.21.2013.12.16.15.06.44 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Mon, 16 Dec 2013 15:06:46 -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: 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:c03::22b 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:8143 Archived-At: On 12/16/13 11:44 PM, Zhihao Yuan wrote: > On Mon, Dec 16, 2013 at 1:35 AM, David Krauss wrote: >> Right now I'm making due with an imperfect constexpr hash: >> [...] >> >> The ud-string-literal is used directly as a non-type template argument, so >> it must have scalar type, which cannot contain more information than a >> std::intmax_t, or else be a reference to global, which seemingly cannot be >> generated suitably. Another way of looking at this is not the need for >> template string arguments, but the need for a non-type template argument >> that can uniquely encode arbitrarily much data, and can be returned from a >> ud-string-literal function. > AFAICS all you are building is a symbol table, then why not ask for a > language feature like, a symbol type? Compiler builds symbol table > cheaper and nicer then you do :) I do also perform the same hash on user input as a proxy for string equality. When this is not required, I use an elaborated-type-specifier for local declaration of a namespace-member, incomplete class. My use case sounds similar to Sean Middleditch's. If the declarations were at namespace scope, and they contained two copies of the literal (likely job for a macro), then the declared objects could have a proper copy of the string to catch collisions. -- --- You received this message because you are subscribed to the Google Groups "ISO C++ Standard - Future Proposals" group. 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