220 31794 <9C5ACBB5-5FF7-495E-9DF4-6DD5E857ED72@gmail.com> article Path: news.gmane.org!.POSTED!not-for-mail From: Alberto Barbati Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: This variable should not be named: an identifier (not) to remember Date: Tue, 28 Mar 2017 08:18:41 +0200 Lines: 175 Approved: news@gmane.org Message-ID: <9C5ACBB5-5FF7-495E-9DF4-6DD5E857ED72@gmail.com> References: <985b9b2a-c734-45eb-95f4-db4dc0d309a1@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 (1.0) Content-Type: multipart/alternative; boundary=Apple-Mail-5B2EAA3A-10BD-41AB-88C8-C0C45CA4A342 Content-Transfer-Encoding: 7bit X-Trace: blaine.gmane.org 1490681935 28949 195.159.176.226 (28 Mar 2017 06:18:55 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Tue, 28 Mar 2017 06:18:55 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCPY5DV6RIMBBREA5DDAKGQEXUKVBZI@isocpp.org Tue Mar 28 08:18:50 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-lf0-f70.google.com ([209.85.215.70]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1cskSl-0005zM-C2 for gclcip-std-proposals@m.gmane.org; Tue, 28 Mar 2017 08:18:39 +0200 Original-Received: by mail-lf0-f70.google.com with SMTP id t132sf33556173lfe.12 for ; Mon, 27 Mar 2017 23:18:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=from:content-transfer-encoding:mime-version:date:subject:message-id :references:in-reply-to: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=f8xwsSVoigOcMcUmVkbr/erG+f/Xy3XLuGrBBTb/fU0=; b=iSfS8YmmGWGJr5z3R28+aEzMvfC3uISLlTo5zbv8D8SfZbfI05lnF7SBnnPPJ633EW PluLcQEjrCBKX043XV8dwRa0JFgyJOMX+a2zUzZ24IE+Nrp3y09GEELbhSBX+hH5ZngG 90FFjeuXUrAOTCc7g4jFC2qAqpwdr1xYUpXUB5RZcSdcb0jkQWae9frHovDHnLjvgsaO oYqwEhuxrfylZJytwQoQ/SNPjZaJmqUotrhT/QkQjh/nzTbdA9CiIb/6QJAmu/wgKoN4 PHu/RyNwUhjKPxEnxZY2TSPccFrH9huwcKn7dU1S8RU1YmYOueOqQg17TyFWoQMkMMzV OMFA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:content-transfer-encoding:mime-version:date :subject:message-id:references:in-reply-to: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=f8xwsSVoigOcMcUmVkbr/erG+f/Xy3XLuGrBBTb/fU0=; b=c5xDJEsnQhQivZGZrQdb9d5+ZFmoW371E09qP/NSC/FRr5ou5lidljNBAQnoBVgol3 1KSkOwo4Hl+iM7/vg2VrwHEr96a6eGEGA9e5pQvYF/b295r8o7Gd8BnuJz4a0SUmFqPC N9+K1zw/CAObK7EqtiMcDSXfXqR2QpvsbAVo8QEemZJAS1zYsn/hxScqxwNWOr0HcdsK SUQPC8+ihE4Bsb4S+uSqpQ6ysjKfxkdxIKpnie6R21Fj59bW1+zH9PoJfOCa2cvtHQas z81SHhgZTk0ZOJqQaGnleU1mr7BQGHqopDWZYDwJdN0t3t1DkwxCo2OIwYlBh0XpkBpX UKD X-Gm-Message-State: AFeK/H1ysO/fHKuzISG3Ki+mw89M+RNh0rbreaqBI2I3DfiYI/RoINhQnRZ4CUQ2XoOcNw== X-Received: by 10.25.72.71 with SMTP id v68mr3588094lfa.9.1490681925565; Mon, 27 Mar 2017 23:18:45 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.28.157.193 with SMTP id g184ls1661005wme.13.gmail; Mon, 27 Mar 2017 23:18:44 -0700 (PDT) X-Received: by 10.28.22.129 with SMTP id 123mr12050758wmw.10.1490681924193; Mon, 27 Mar 2017 23:18:44 -0700 (PDT) Original-Received: from mail-wr0-x241.google.com (mail-wr0-x241.google.com. [2a00:1450:400c:c0c::241]) by mx.google.com with ESMTPS id m42si3460524wrm.252.2017.03.27.23.18.44 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 27 Mar 2017 23:18:44 -0700 (PDT) Received-SPF: pass (google.com: domain of albertobarbati@gmail.com designates 2a00:1450:400c:c0c::241 as permitted sender) client-ip=2a00:1450:400c:c0c::241; Original-Received: by mail-wr0-x241.google.com with SMTP id p52so16426537wrc.2 for ; Mon, 27 Mar 2017 23:18:44 -0700 (PDT) X-Received: by 10.28.107.129 with SMTP id a1mr7614043wmi.47.1490681923581; Mon, 27 Mar 2017 23:18:43 -0700 (PDT) Original-Received: from [172.20.10.6] ([91.252.4.165]) by smtp.gmail.com with ESMTPSA id k128sm2165147wmf.16.2017.03.27.23.18.42 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 27 Mar 2017 23:18:43 -0700 (PDT) In-Reply-To: X-Mailer: iPad Mail (14D27) X-Original-Sender: AlbertoBarbati@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com; spf=pass (google.com: domain of albertobarbati@gmail.com designates 2a00:1450:400c:c0c::241 as permitted sender) smtp.mailfrom=albertobarbati@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:31794 Archived-At: --Apple-Mail-5B2EAA3A-10BD-41AB-88C8-C0C45CA4A342 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Hi Chris, Even if it cannot be referenced again, a __ variable is still a variable an= d therefore it ends its lifetime at the end of the lexical scope. Its destr= uctor is therefore called when the scope is exited either normally or excep= tionally and no sooner. This is the main point of the RAII idiom. On the ot= her hand, `Foo{bar};` creates a temporary object that is immediately destro= yed at the end of the statement. Cheers, Alberto > Il giorno 27 mar 2017, alle ore 22:51, Christopher Di Bella ha scritto: >=20 > Hi, >=20 > Thanks for taking the time out to write this! It seems like there is moti= vation, but I can't quite place my finger on it. If a variable isn't going = to be used again, and can't be referenced, what are the benefits of its per= sistence have over `Foo{bar};`? >=20 > Cheers, >=20 > Chris >=20 >=20 >> On Tue., 28 Mar. 2017, 07:27 Alberto Barbati, = wrote: >> Hello, >>=20 >> this is a draft for a proposal to add a special meaning to the identifie= r __ (double underscore) so that it can be used (even repeatedly in the sam= e lexical scope) for all variables whose name is not important and that is = no longer needed after declaration. The draft includes a few examples. >>=20 >> Is there any interest in this? >>=20 >> Thanks in advance, >>=20 >> Alberto >>=20 >> --=20 >> You received this message because you are subscribed to the Google Group= s "ISO C++ Standard - Future Proposals" group. >> To unsubscribe from this group and stop receiving emails from it, send a= n 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/iso= cpp.org/d/msgid/std-proposals/985b9b2a-c734-45eb-95f4-db4dc0d309a1%40isocpp= ..org. >=20 > --=20 > You received this message because you are subscribed to a topic in the Go= ogle Groups "ISO C++ Standard - Future Proposals" group. > To unsubscribe from this topic, visit https://groups.google.com/a/isocpp.= org/d/topic/std-proposals/BTVwFqDkhXk/unsubscribe. > To unsubscribe from this group and all its topics, send an email to std-p= roposals+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/isoc= pp.org/d/msgid/std-proposals/CACL3gUVC1R9occL7vwiNTb9s4rD-%2Baemb4AprquTjQv= r-xRjwg%40mail.gmail.com. --=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/9C5ACBB5-5FF7-495E-9DF4-6DD5E857ED72%40gmail.com= .. --Apple-Mail-5B2EAA3A-10BD-41AB-88C8-C0C45CA4A342 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
Hi Chris,
Even if it cannot be referenced again, a __ variable is still a= variable and therefore it ends its lifetime at the end of the lexical scop= e. Its destructor is therefore called when the scope is exited either norma= lly or exceptionally and no sooner. This is the main point of the RAII idio= m. On the other hand, `Foo{bar};` creates a temporary object that is immedi= ately destroyed at the end of the statement.

Cheer= s,

Alberto

Il giorno 27 mar 2017, al= le ore 22:51, Christopher Di Bella <cjdb.ns@gmail.com> ha scritto:

Hi,

Thanks for taking the time out to write this! It seems like = there is motivation, but I can't quite place my finger on it. If a variable= isn't going to be used again, and can't be referenced, what are the benefi= ts of its persistence have over `Foo{bar};`?

Cheers,

Chris


On Tue., 28 Mar. 2017, 07:2= 7 Alberto Barbati, <albertob= arbati@gmail.com> wrote:
Hello,

this is a draft for a proposal to add a special meaning to t= he identifier __ (double underscore) so that it can be used (even repeatedl= y in the same lexical scope) for all variables whose name is not important = and that is no longer needed after declaration. The draft includes a few ex= amples.

Is there any interes= t in this?

Thanks in advance= ,

Alberto

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