220 30474 article Path: news.gmane.org!.POSTED!not-for-mail From: Peter Koch Larsen Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: enum_cast proposal Date: Wed, 11 Jan 2017 08:58:03 +0100 Lines: 43 Approved: news@gmane.org Message-ID: References: <57258435-5d82-48e7-8ed7-3c38682418fb@isocpp.org> <58750288.5080004@gmail.com> <5875286B.7040604@gmail.com> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-Trace: blaine.gmane.org 1484121486 29179 195.159.176.226 (11 Jan 2017 07:58:06 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Wed, 11 Jan 2017 07:58:06 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDRIBXXKZQERBDGL27BQKGQE6CNOXSQ@isocpp.org Wed Jan 11 08:58:02 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-it0-f71.google.com ([209.85.214.71]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1cRDnE-0006zw-Ke for gclcip-std-proposals@m.gmane.org; Wed, 11 Jan 2017 08:58:00 +0100 Original-Received: by mail-it0-f71.google.com with SMTP id p189sf152650562itg.2 for ; Tue, 10 Jan 2017 23:58:05 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :x-original-sender:x-original-authentication-results:reply-to :precedence:mailing-list:list-id:x-spam-checked-in-group:list-post :list-help:list-archive:list-subscribe:list-unsubscribe; bh=42FmYhh91mZT3K2JOHEAiJj8qTO3LKnAIbEvec7jOW0=; b=KvXnuDiZXLrH7BW42Alf3gQ1EaxxYZ0HhuNglzSDNWbrKH3wa9Hnjjb4n4xx6/o9n5 rUpNMMNVbfJ3spUXsj9t6nTBhbJMfenA2e6H5gqJYSLb4sU5X5XqBpa0kWBLuznflCsY 7gkF4foLXyOXk6UHZ7wHvUAuRvEDec+ptQrQx6SK2wb52QcOFiiwmFibCcSEV6DORdL3 oVRR5+Y2nPMNklvCgjfzHFzGbmWqrPeaNr8wYopOjPpQaJ8TK6S3CcUk2zl7PI0JJLJT XmvH3dafnQgAZbkcRxAYzvA8Bt5PEZ9pz6iVY66HtJ3UPyDIavczANM84MlZCKnAXCv1 UZkw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:x-original-sender :x-original-authentication-results:reply-to:precedence:mailing-list :list-id:x-spam-checked-in-group:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=42FmYhh91mZT3K2JOHEAiJj8qTO3LKnAIbEvec7jOW0=; b=GZCR/DTSOdkwOsAFfwT9U7jNCmmrtrqrx8iyR6ZAe06f4R+N42kTVK3Km4x5mQUfY4 8ntdXZRprQpi1JzEm5+DyzKVFxIC8lguNfwOze2F0Hyd657t58CusOe189uUTpNcLmHf vl+Z5l/VspMULJDERMvt6qBh8f+wCwyLdu03TB0Uv2rn4Ds+4j+vHWMAty0RQV5CFp5j l1qljuM9j7QQHcaTZ4c9kKDowCMA8sAD4uTGDeu9pLacpD3BWbiHZMiXht7CN9sFw5sZ C5marO/5cKTv5VdpayKlLNVk8wvi4QY09sSITQtCkHJhN4BmVPsxoH1vcbj9qu4/Fd2N dOTw== X-Gm-Message-State: AIkVDXKmmPhyCphMv4db+BdM+bqNStJK/TilAALVPD8D+V/J2ML6QT0ryFkrjZZBWknShg== X-Received: by 10.36.39.196 with SMTP id g187mr5130221ita.14.1484121484940; Tue, 10 Jan 2017 23:58:04 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.157.5.41 with SMTP id 38ls855107otw.35.gmail; Tue, 10 Jan 2017 23:58:04 -0800 (PST) X-Received: by 10.176.3.196 with SMTP id 62mr3376561uau.120.1484121484315; Tue, 10 Jan 2017 23:58:04 -0800 (PST) Original-Received: from mail-ua0-x234.google.com (mail-ua0-x234.google.com. [2607:f8b0:400c:c08::234]) by mx.google.com with ESMTPS id d13si762078uag.37.2017.01.10.23.58.04 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 10 Jan 2017 23:58:04 -0800 (PST) Received-SPF: pass (google.com: domain of peter.koch.larsen@gmail.com designates 2607:f8b0:400c:c08::234 as permitted sender) client-ip=2607:f8b0:400c:c08::234; Original-Received: by mail-ua0-x234.google.com with SMTP id 96so80642767uaq.3 for ; Tue, 10 Jan 2017 23:58:04 -0800 (PST) X-Received: by 10.176.71.5 with SMTP id h5mr3956590uac.167.1484121483972; Tue, 10 Jan 2017 23:58:03 -0800 (PST) Original-Received: by 10.103.11.5 with HTTP; Tue, 10 Jan 2017 23:58:03 -0800 (PST) In-Reply-To: <5875286B.7040604@gmail.com> X-Original-Sender: peter.koch.larsen@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com; spf=pass (google.com: domain of peter.koch.larsen@gmail.com designates 2607:f8b0:400c:c08::234 as permitted sender) smtp.mailfrom=peter.koch.larsen@gmail.com; dmarc=pass (p=NONE sp=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:30474 Archived-At: On Tue, Jan 10, 2017 at 7:31 PM, Matthew Woehlke wrote: > On 2017-01-10 12:01, Peter Koch Larsen wrote: >> What do you do if you have an enum with some same_valued elements >> (enum E { ea = 0, eb = 0})? My implementation forbids this. > > Why? > > E x = ea; > assert(x == eb); // will succeed > > Such a prohibition makes some sense when converting an enum to a string > (or to its ordinal), but there is no problem when converting an int to > an enum (or a string to an enum, for that matter). This is exactly my problem. I partially use my library in to do this stuff, and it could be confusing for the user if you serialize as ea and get eb back. I also have a bitset class (enum_bitset), where I as a template parameter define if i set the bit depending on the underlying enums ordinal values or by its underlying integral value. In neither case do I see any use of having two enums with the same value. Also, I do not see a reason in have two enums with the same value. Before my library, I would have two underlying enums with the same value in two situations: To have a count (e.g. enum color { red,green,blue, color_count = blue} or to name bit-sets enum state { created = 1, received = 2, sent = 4, active = created}). These reasons are both gone now. /Peter > > -- > Matthew > -- 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/CANPtknxx9BXfwLagcO1ucu4pwi6PS6ewrdPzQsqOXgPUGuR-og%40mail.gmail.com. .