220 30463 <587512E1.1050708@gmail.com> article Path: news.gmane.org!.POSTED!not-for-mail From: Matthew Woehlke Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: enum_cast proposal Date: Tue, 10 Jan 2017 11:59:13 -0500 Lines: 37 Approved: news@gmane.org Message-ID: <587512E1.1050708@gmail.com> References: <57258435-5d82-48e7-8ed7-3c38682418fb@isocpp.org> <58750288.5080004@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 1484067559 1079 195.159.176.226 (10 Jan 2017 16:59:19 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Tue, 10 Jan 2017 16:59:19 +0000 (UTC) User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0 To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBC37LBFWUIFBBY5F2TBQKGQELLUN6NI@isocpp.org Tue Jan 10 17:59:14 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-pf0-f199.google.com ([209.85.192.199]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1cQzlP-0007zn-W2 for gclcip-std-proposals@m.gmane.org; Tue, 10 Jan 2017 17:59:12 +0100 Original-Received: by mail-pf0-f199.google.com with SMTP id z128sf292424036pfb.4 for ; Tue, 10 Jan 2017 08:59:16 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=subject:to:references:from:message-id:date:user-agent:mime-version :in-reply-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=ziQDTDDLjjsfR17N75ISVMUKHNYoh/uAmU/JIqOMIRk=; b=zmahQr4KMwqhVgi6D7nUsEP2YsgwFVtxM6GAe9n8DSB6AoRPwbbn0txhe2CSCTbPNp LlukwliivEoC5SC/szMNoZvcCs9etO+j/kxipuBaHApCIthZsR/Nvk7ofDpwwaFn7Yt7 dTWwivJcMRXwruEhyAvTmkPjT3DfaBKQfOKfB3ruIUMJjb66orl+bPnEV9nXFV26cTDT 9XjZCI1hbrE2WslEsRMF4/lMz0L+qPobbsLgW/KRnkdcnahmtz8TfogfuzN+hoIKDQdK EBc5tdHyjEvk5o99zLPUWPVxk4LLCVnZp3VTVc6ANt43FRiY7ZEFnf+GSI9shmhcwZQZ z41w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:references:from:message-id:date :user-agent:mime-version:in-reply-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=ziQDTDDLjjsfR17N75ISVMUKHNYoh/uAmU/JIqOMIRk=; b=nLvfe9/VIeEa5mhnifTwE1226nMlg7yLVa0qIv23ErXEOx91zKMD0p9z7mQR2aCCuq W9Nj7MQW1MIEXvmO+JwsmgyKPCUW6sAZJHpcFqsd70R7vK2N8gK06Yn0BFYCYhNdEtTp 5UXxnFr+3Zd3T/J7f+uZewzd/v+ZUfXkXr1nsmcIwYFdhh62BDvGG0vEjKHNQdh661yM h4A1WvU3U60kw+qWbSn3HSziHhM2SbJzvhQbMJQoqQvBVqr9XLv2x5uZdm4hOu4UjRUb a8QQXCiEaVgbVr09HE8DukZwdBd6oLnHcILy2+poAcvogjPRwJbsNxW5CU1pHOPdQMDB JoXg== X-Gm-Message-State: AIkVDXIXPwoV+kOizApPD5RRa9pCa1MTC3eB4Kcsol0BGNSWvXKTMy8pc16vMWECCGa5Qg== X-Received: by 10.98.218.85 with SMTP id w21mr177620pfl.41.1484067555863; Tue, 10 Jan 2017 08:59:15 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.157.17.154 with SMTP id v26ls1993923otf.0.gmail; Tue, 10 Jan 2017 08:59:15 -0800 (PST) X-Received: by 10.37.125.131 with SMTP id y125mr896132ybc.192.1484067555279; Tue, 10 Jan 2017 08:59:15 -0800 (PST) Original-Received: from mail-yw0-x22b.google.com (mail-yw0-x22b.google.com. [2607:f8b0:4002:c05::22b]) by mx.google.com with ESMTPS id n4si769149ywe.234.2017.01.10.08.59.15 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 10 Jan 2017 08:59:15 -0800 (PST) Received-SPF: pass (google.com: domain of mwoehlke.floss@gmail.com designates 2607:f8b0:4002:c05::22b as permitted sender) client-ip=2607:f8b0:4002:c05::22b; Original-Received: by mail-yw0-x22b.google.com with SMTP id l19so7954795ywc.2 for ; Tue, 10 Jan 2017 08:59:15 -0800 (PST) X-Received: by 10.13.206.132 with SMTP id q126mr3670927ywd.311.1484067554813; Tue, 10 Jan 2017 08:59:14 -0800 (PST) Original-Received: from [192.168.1.173] (tripoint.kitware.com. [66.194.253.20]) by smtp.googlemail.com with ESMTPSA id x185sm1140329ywe.35.2017.01.10.08.59.13 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 10 Jan 2017 08:59:14 -0800 (PST) In-Reply-To: X-Original-Sender: mwoehlke.floss@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com; spf=pass (google.com: domain of mwoehlke.floss@gmail.com designates 2607:f8b0:4002:c05::22b as permitted sender) smtp.mailfrom=mwoehlke.floss@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:30463 Archived-At: On 2017-01-10 11:20, Nicol Bolas wrote: > On Tuesday, January 10, 2017 at 10:49:34 AM UTC-5, Matthew Woehlke wrote: >> On 2017-01-10 10:31, m.ce...@gmail.com wrote: >>> For sure baseline API must be exception-free. >>> Do we really want to additionally support API that throws on error? >> >> I *really* hope we can use something like std::expected; this is a >> textbook use case for that, and makes it trivial to have a >> throw-on-error API (just grab the value from the expected without >> checking it first; this will turn around and throw if the value is not >> there). > > But the fact that it's throwing the wrong exception makes it useless from > an exception handling perspective. Huh? I'm talking about std::expected, not std::optional. If you didn't get a value, you get whatever error/exception (preferably an exception in this case, since it doesn't need more storage than the enum and thus doesn't cost extra) the API stuffed in instead, which would presumably be a std::range_error or std::bad_enum_cast or whatever. IOW, the *SAME* exception that an API that throws right away would throw. > * `enum_cast`: Converts to the enumeration type, or throws if it cannot. > * `enum_cast_opt`: Returns an `optional`. These can be combined with no loss of function into one API that returns a std::expected or similar. -- 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. 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