220 30175 <2998762.etaySSRi7N@tjmaciei-mobl1> article Path: news.gmane.org!.POSTED!not-for-mail From: Thiago Macieira Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: enum_cast proposal Date: Tue, 03 Jan 2017 13:56:30 -0200 Lines: 53 Approved: news@gmane.org Message-ID: <2998762.etaySSRi7N@tjmaciei-mobl1> References: <1483532086.2yCkjVBYWJ@tjmaciei-mobl1> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Trace: blaine.gmane.org 1483459003 30240 195.159.176.226 (3 Jan 2017 15:56:43 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Tue, 3 Jan 2017 15:56:43 +0000 (UTC) User-Agent: KMail/5.3.3 (Linux/4.8.13-1-default; KDE/5.28.0; x86_64; ; ) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCB4TK757YBRBMUTV7BQKGQEZ6QIFQI@isocpp.org Tue Jan 03 16:56:34 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-wj0-f198.google.com ([209.85.210.198]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1cORRv-0006OS-5C for gclcip-std-proposals@m.gmane.org; Tue, 03 Jan 2017 16:56:31 +0100 Original-Received: by mail-wj0-f198.google.com with SMTP id iq1sf50452648wjb.1 for ; Tue, 03 Jan 2017 07:56:35 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=from:to:subject:date:message-id:user-agent:in-reply-to:references :mime-version:content-transfer-encoding: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=tsN/6QbintzU+m13NQUEsJTknUgb0LBSFRDoQMF5qpU=; b=oQCnQyUO0e47sOoWFUW0iiLdj9w6P8mGQjs+eTcB+ZEdZhSpM91toBouYumW/nLY8G /dRF4hyH30s+82y5TFvPhPpfB7dUyBPOu/wMym+Q9guYfQs1fG/HBa/A5klx7lLcjl5v 8lF3eWkxhp0yUj4jT4+xswJVCSJCUYz2R6oxROsMXbO5fmFkx6wNsr7V8lv5+y1iVxhc 2bcK6DRcgwdhhJK/OsOmzfm469YC8BdAckC+nwM2x2+37Tf3RmIf5K2XFJOzX5shRlA2 Wt/uQ2PVOr3oaIQrK55EA/Q3ZPF8nMST5bLmVlQrWSbVML475FsqyKAyvJW2VvFwIoYG X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:subject:date:message-id:user-agent :in-reply-to:references:mime-version:content-transfer-encoding :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=tsN/6QbintzU+m13NQUEsJTknUgb0LBSFRDoQMF5qpU=; b=mXnVgjwkIW1rJM/l736TdwFIfYz54HET6o4l7EpLzvvcAN+1nwTTA1G1NGCyfcNUUE Ca84UiQyZ+Mwig6NzQZQ4SKlpgFl5dKQiU00BtomG94eV4KHWI7dxoyKLvS/kKooxZSi OXYJgDcbNUXlEHg+rpsUQ2mmixDiQ1Q718VPdakvlMJvTg2NA7jM92xiYmo6KpDw01Ip CYthcO1JB0hmbSTbFHegaYuiP5lkE7Ja6x3Q9vJIkqOrRciL/lbv1nMmVyUoa3QEIAjn xAod7Nu7X8OQTUDEOrdAwubXf7C4clnpX4Fyfhf8YTzEXUG4H8Z09ENyFfylveXDIjWz X-Gm-Message-State: AIkVDXInx5J+62zpRh80iXJ7BjEMBRl3GnqbUKdnIjxNk/cvS+cwGT0WPC8kIrbWa2fHvw== X-Received: by 10.28.23.207 with SMTP id 198mr1568621wmx.0.1483458995301; Tue, 03 Jan 2017 07:56:35 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.28.157.71 with SMTP id g68ls5972183wme.27.canary-gmail; Tue, 03 Jan 2017 07:56:34 -0800 (PST) X-Received: by 10.194.99.38 with SMTP id en6mr54696013wjb.184.1483458994240; Tue, 03 Jan 2017 07:56:34 -0800 (PST) Original-Received: from gondolin.macieira.info (gondolin.macieira.info. [78.47.120.188]) by mx.google.com with ESMTP id b197si74017617wme.159.2017.01.03.07.56.34 for ; Tue, 03 Jan 2017 07:56:34 -0800 (PST) Received-SPF: pass (google.com: domain of thiago@macieira.org designates 78.47.120.188 as permitted sender) client-ip=78.47.120.188; Original-Received: from tjmaciei-mobl1.localnet (unknown [187.34.234.250]) by gondolin.macieira.info (Postfix) with ESMTPSA id 34DBA11B7E9 for ; Tue, 3 Jan 2017 07:56:33 -0800 (PST) In-Reply-To: X-Original-Sender: thiago@macieira.org X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of thiago@macieira.org designates 78.47.120.188 as permitted sender) smtp.mailfrom=thiago@macieira.org 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:30175 Archived-At: On ter=C3=A7a-feira, 3 de janeiro de 2017 07:06:10 BRST m.cencora@gmail.com= wrote: > Compiler should synthesize a function like below: >=20 > optional enum_cast(int x) > { > switch(x) > { > case red: > case green: > case blue: > return static_cast(x); > default: > return nullopt; > } > } How do you know whether a use of enum_cast is compile-time or whether it is= =20 runtime? static_cast is always compile time and always succeeds or produces a=20 compilation error. Therefore, checking at runtime is unnecessary. dynamic_cast is almost always runtime and its result needs to be checked at= =20 runtime. Also, where did that optional come from? If it's going to use optional, the= n=20 it needs to be a library feature. > Of course it could implement it more efficently (as range check instead o= f > switch if all enumerators are consecutive integers). One would expect the compilers to be smart enough to do that with a switch= =20 block that is contiguous. Still, QoI issue. --=20 Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org Software Architect - Intel Open Source Technology Center --=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. To view this discussion on the web visit https://groups.google.com/a/isocpp= ..org/d/msgid/std-proposals/2998762.etaySSRi7N%40tjmaciei-mobl1. .