220 24595 article Path: news.gmane.org!not-for-mail From: Dmitry Banschikov Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: throwaway variable Date: Mon, 22 Feb 2016 21:47:13 +0300 Lines: 57 Approved: news@gmane.org Message-ID: References: <9658e852-6254-4ecf-a6d4-879160d4de7d@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Trace: ger.gmane.org 1456166847 9171 80.91.229.3 (22 Feb 2016 18:47:27 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Mon, 22 Feb 2016 18:47:27 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDWPB7UGWEIBBM5PVW3AKGQE3VHXIDY@isocpp.org Mon Feb 22 19:47:22 2016 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-io0-f199.google.com ([209.85.223.199]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1aXvVu-0000tK-0k for gclcip-std-proposals@m.gmane.org; Mon, 22 Feb 2016 19:47:18 +0100 Original-Received: by mail-io0-f199.google.com with SMTP id t64sf361593881ioe.0 for ; Mon, 22 Feb 2016 10:47:17 -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:date:message-id:subject:from:to :content-type: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=DpHvhIQYvq0RJh+AevIyJg92zGK1ZKF7KDj9TBmHWyU=; b=HuDIj9AiGxCXPRMW/tFFWg12WV0bxz/9Qeg0+/BRBp3nsIjTEOnP3x/olVtvL/lLlI r+9shcVtx2Tx5LLbNe8IA3vwdz3kxXPtU4jEtQ/0t6ezJ9sQ9Zqtw1vqYOcw2Gx8NIQH +nrG+1Guy+4JZlV6Ies00Rf3A2fyNlbgQb24p9mRWv3AbGiOXvarXLfpO1+9GA4rZIsh IlElp31UUlwQb9eglmthleQkB+54MarW9ss222qmB+X4Wl0Rzy3kyUtxZe7i4osE6L33 5gr/+ac9cpIODn6DtCVU7oJ6itkxLCGyd91C6zUdZOm+Ny8sadpSYr/u8fkfuYH/nfVa X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:date :message-id:subject:from:to:content-type: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=DpHvhIQYvq0RJh+AevIyJg92zGK1ZKF7KDj9TBmHWyU=; b=eOqlYhLojiPXsCI5QoLqczhhfNVpQdSUVEMu/umxKQ8TFoF5hRJaqzgKjzsKhxbtuQ +UBEEB3QBI5W7zEUWpgIrMejVaW2OF572V1hvTmWwiYRGhDsJXRHx3tTceg9ah+NTfN3 pLXY+N3+K+EeMG5gaYjWvpGk6WmpVQhRPPMhVigViWQBfcK5o6NFwrUF4/NpFdHA1HRQ BeusrbcXZWKPbdbeOIzO8U9yTNu7VWI0yn6mszVZef6/wIgAV5HXVPMtjfat17wV++C6 n69ohGZxUoeKBvxftnEnhFD6fPiqlySy31IJxQq1Sr5SOqSalw3GGOCUOsXBFZ+23Ynd X-Gm-Message-State: AG10YOTq6iGpJ7pIhlzBmtjqiBBs4y1WHbnPeJ3sPU56GEWyoF69nvTlG1vkP2Cfj4tBnA== X-Received: by 10.182.255.203 with SMTP id as11mr29849203obd.49.1456166836996; Mon, 22 Feb 2016 10:47:16 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.140.22.202 with SMTP id 68ls1441690qgn.3.gmail; Mon, 22 Feb 2016 10:47:15 -0800 (PST) X-Received: by 10.129.84.70 with SMTP id i67mr16363980ywb.16.1456166835072; Mon, 22 Feb 2016 10:47:15 -0800 (PST) Original-Received: from mail-yk0-x235.google.com (mail-yk0-x235.google.com. [2607:f8b0:4002:c07::235]) by mx.google.com with ESMTPS id e124si11896282ywf.300.2016.02.22.10.47.14 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 22 Feb 2016 10:47:14 -0800 (PST) Received-SPF: neutral (google.com: 2607:f8b0:4002:c07::235 is neither permitted nor denied by best guess record for domain of me@ubique.spb.ru) client-ip=2607:f8b0:4002:c07::235; Original-Received: by mail-yk0-x235.google.com with SMTP id z13so65416938ykd.0 for ; Mon, 22 Feb 2016 10:47:14 -0800 (PST) X-Received: by 10.37.33.8 with SMTP id h8mr14375550ybh.175.1456166834166; Mon, 22 Feb 2016 10:47:14 -0800 (PST) Original-Received: by 10.37.104.5 with HTTP; Mon, 22 Feb 2016 10:47:13 -0800 (PST) In-Reply-To: X-Original-Sender: me@ubique.spb.ru X-Original-Authentication-Results: mx.google.com; spf=neutral (google.com: 2607:f8b0:4002:c07::235 is neither permitted nor denied by best guess record for domain of me@ubique.spb.ru) smtp.mailfrom=me@ubique.spb.ru; dkim=pass header.i=@ubique-spb-ru.20150623.gappssmtp.com Precedence: list Mailing-list: list std-proposals@isocpp.org; contact std-proposals+owners@isocpp.org List-ID: X-Spam-Checked-In-Group: std-proposals@isocpp.org 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:24595 Archived-At: On Mon, Feb 22, 2016 at 8:56 PM, Matthew Woehlke wrote: > On 2016-02-22 12:00, Viacheslav Usov wrote: >> On Mon, Feb 22, 2016 at 4:35 PM, Matthew Woehlke wrote: >>> On 2016-02-21 08:55, Viacheslav Usov wrote: >>>> On Fri, Feb 19, 2016 at 9:06 PM, Patrice Roy wrote: >>>>> I often use _ as =C2=ABuninteresting but needed=C2=BB variables such = as >>>>> lock_guards. Please don't break my code :) >>>> >>>> I would even say that this case, "uninteresting but needed" is >>>> more interesting. It would be nice to have a language construct >>>> that creates an "anonymous" variable in the current scope. >>>> Alternatively, this could be conceptualized as a temporary whose >>>> lifetime is extended till the end of the current scope. >>> >>> Is that not what we're proposing? >> >> I am not sure. The discussion definitely started with a very different >> idea, and I do not think I saw a clear statement similar to what I wrote >> above. > > I'm not sure I'd call it "different" or not. The OP (who curiously seems > to have dropped out of the conversation) originally only mentioned being > implicitly `[[maybe_unused]]`. Ville immediately brought up > http://cplusplus.github.io/EWG/ewg-active.html#35, which dealt with > "nameless" variables, which seems consistent with the OP's intent as > well as much more useful (though Dmitry brings up the interesting point > that these should be `[[maybe_unused]]`, now that that seems likely to > be in C++17). I've generally read the rest of the thread as referring to > such 'anonymous variables'. I haven't dropped conversation, just listening for opinions. My initial desire was to have something like blank identifier in Go or _ variable in Python. Actually, I have got construct that works but looks ugl= y: for(auto attempt [[gnu::unused]] : {1,2,3}) { .. . . } Possibly standard [[unused]] attribute specifier will make a sense. The idea to have a "__" seems to me as orthogonal one(and for sure useful) = and having implicit unused attribute may be not appropriate for it. --=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/CABuNDZSXRcaZPoYGSbcCLK1x3p70jzxLCeuVO07Mpu%3DD4= 1M5tw%40mail.gmail.com. .