220 24591 article Path: news.gmane.org!not-for-mail From: Viacheslav Usov Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: throwaway variable Date: Mon, 22 Feb 2016 18:00:34 +0100 Lines: 103 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: multipart/alternative; boundary=001a113e24b47423a7052c5ec59c X-Trace: ger.gmane.org 1456160438 29265 80.91.229.3 (22 Feb 2016 17:00:38 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Mon, 22 Feb 2016 17:00:38 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDU6VRPKW4BBBM75VS3AKGQEI2JBGCY@isocpp.org Mon Feb 22 18:00:38 2016 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-ig0-f197.google.com ([209.85.213.197]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1aXtqf-0000kf-2Q for gclcip-std-proposals@m.gmane.org; Mon, 22 Feb 2016 18:00:37 +0100 Original-Received: by mail-ig0-f197.google.com with SMTP id dp10sf314619100igc.0 for ; Mon, 22 Feb 2016 09:00:36 -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: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=laZ5JIfIZJXVZ0OBh9aGrfIDt7VVEbjCeEf2a0LzWoE=; b=a8jqCYlK5X7ULj5CuCJNSmBJnqPkDYvimTGzMhkGXCpZtEDelsujc9Y281hdvN2mNS Mt2LY82Q9P6gcJM13n2+ZoQwkFUNhQeRfoeL/K2rjckdPDNvnNJBGMqvfH0eJ+qu48ES /uYJgKZRRkRQkeoa9CTcdyICD9KeVTwVvY2DVh7tAUzNcVp7HSxepcCfOj3TeWgrAcrt 09zIUXdIz5uEbIDKhazYL7yOX7MCcGK1Jzub2Nk9+71NFKQnPoWSBuZvW9BqxGIzHv8R LY8rGOPRn5+bObeJoxfFjUxRb48wyn19VgZAADxEi+jm1E3TiDF342XbeQGUNFx1BQt2 /eCQ== 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: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=laZ5JIfIZJXVZ0OBh9aGrfIDt7VVEbjCeEf2a0LzWoE=; b=dfI0dJZCK4qr5n/2UIJlodel9XlR87f4QqnQ0QhYg+pu4nLdRQ31OWmFhy8ZNeI95k DCydVSIDsBTN1ldtGLpmJwzbFd+X84opEKp1SkfJamL8Hwm6skhfHnjcETpMvoZzjh+K G7B3kIgsZGJMB4CqZrBHQMqd1bemxrpajnEusPdzrP4mVvzgLq8LJDTFIf3IP9/OkbnL OxQoYeKdAg07SAWQ7ZXcTAttOMdJ/+TQ5jnBSe57vdj5IEP6MtRYjMoghgCgFBnbPlEI v8aCcrtidotCBOKhnrVHZbkEN1ivjmZBVL6noBtizJvpUbXxHtDL+M13pBJjhpdWOcmd bT0g== X-Gm-Message-State: AG10YOQkKcby21hhZ9D9sKG4UGtAkA4zhYRjP1ugYf4Ck9vlj1pn0AmDphyMnEVHxdmYKw== X-Received: by 10.182.254.35 with SMTP id af3mr27092691obd.37.1456160436200; Mon, 22 Feb 2016 09:00:36 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.182.66.132 with SMTP id f4ls878005obt.88.gmail; Mon, 22 Feb 2016 09:00:35 -0800 (PST) X-Received: by 10.182.106.13 with SMTP id gq13mr24408325obb.38.1456160435043; Mon, 22 Feb 2016 09:00:35 -0800 (PST) Original-Received: from mail-oi0-x234.google.com (mail-oi0-x234.google.com. [2607:f8b0:4003:c06::234]) by mx.google.com with ESMTPS id s3si304822oex.18.2016.02.22.09.00.35 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 22 Feb 2016 09:00:35 -0800 (PST) Received-SPF: pass (google.com: domain of via.usov@gmail.com designates 2607:f8b0:4003:c06::234 as permitted sender) client-ip=2607:f8b0:4003:c06::234; Original-Received: by mail-oi0-x234.google.com with SMTP id j125so59913089oih.0 for ; Mon, 22 Feb 2016 09:00:35 -0800 (PST) X-Received: by 10.202.196.17 with SMTP id u17mr22776469oif.122.1456160434821; Mon, 22 Feb 2016 09:00:34 -0800 (PST) Original-Received: by 10.76.170.70 with HTTP; Mon, 22 Feb 2016 09:00:34 -0800 (PST) In-Reply-To: X-Original-Sender: via.usov@gmail.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of via.usov@gmail.com designates 2607:f8b0:4003:c06::234 as permitted sender) smtp.mailfrom=via.usov@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-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:24591 Archived-At: --001a113e24b47423a7052c5ec59c Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable 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 a= s > >> 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 o= f > > 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. For the record, I dislike the special names that have been proposed. I believe the lifetime-extended temporary approach is more appropriate, so this should probably be phrased in a language involving temporaries; say if produces a temporary, then & makes it an anonymous variable (and an l-value) in the current scope. The use of & is just an example and not essential. Cheers, V. --=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/CAA7YVg2QppYXRg-zGEnD4%2Bm5yET4fisd0BhXLyGwMaRZg= Ne6tQ%40mail.gmail.com. --001a113e24b47423a7052c5ec59c Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
On M= on, Feb 22, 2016 at 4:35 PM, Matthew Woehlke <mwoehlke.floss@gmail= ..com> wrote:
On 2016-02-21 08:55, Viaches= lav 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 su= ch 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 create= s an
> "anonymous" variable in the current scope. Alternatively, th= is 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.<= /div>

For the record, I dislike the special names that h= ave been proposed. I believe the lifetime-extended temporary approach is mo= re appropriate, so this should probably be phrased in a language involving = temporaries; say if <expression> produces a temporary, then &<= expression> makes it an anonymous variable (and an l-value) in the curre= nt scope. The use of & is just an example and not essential.
=
Cheers,
V.

--
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