220 37567 <20180330054757.GA2396@noemi> article Path: news.gmane.org!.POSTED!not-for-mail From: Magnus Fromreide Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: add the metafunction scope Date: Fri, 30 Mar 2018 07:47:57 +0200 Lines: 46 Approved: news@gmane.org Message-ID: <20180330054757.GA2396@noemi> References: <5e47cc81-4834-4a68-8925-717fb2ec8612@isocpp.org> 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 1522388757 8300 195.159.176.226 (30 Mar 2018 05:45:57 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Fri, 30 Mar 2018 05:45:57 +0000 (UTC) User-Agent: Mutt/1.9.2 (2017-12-15) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDELLREETMBRBEE767KQKGQEBI75WJQ@isocpp.org Fri Mar 30 07:45:53 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-lf0-f71.google.com ([209.85.215.71]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1f1mrJ-00025a-DW for gclcip-std-proposals@m.gmane.org; Fri, 30 Mar 2018 07:45:53 +0200 Original-Received: by mail-lf0-f71.google.com with SMTP id x143-v6sf2410743lff.22 for ; Thu, 29 Mar 2018 22:48:01 -0700 (PDT) ARC-Seal: i=2; a=rsa-sha256; t=1522388881; cv=pass; d=google.com; s=arc-20160816; b=O3UOYcOjwPco4ODYAhP/KUUhsp9NP2xrpquJuo5eOAQtiIHWct9uodc+Z2m09spf38 BjoV6TFfixRhxjEsysUPSGp8gjStzH5PoaiNOn7gczYJbDmJtVnijDLz7B/YLU2+iFMf W4Gz3IAlQmtaPVZUGmXwiWOPs9zqn0eiBLURyqHQAlFqN6dAeiixlynvIkyZjhIzB66p gx9ECLW4avcFJyX8uIdjE+cpGaUcr7lO8xrCboYwSpQhgrH9o+NINkTHK0h1ZqJ7FZBp xokVva7nR0swt1LMaeZ08vaX2WeqByqxgragB7MA4KH1fb4swifzNsinZ2wrdY/+ZlQx egSQ== ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-unsubscribe:list-subscribe:list-archive:list-help:list-post :list-id:mailing-list:precedence:reply-to:user-agent:in-reply-to :content-disposition:mime-version:references:mail-followup-to :message-id:subject:to:from:date:arc-authentication-results :arc-message-signature:dkim-signature:arc-authentication-results; bh=ubNU1M9CizZO6oRO0onstl0qa8tILrqRkgXaJwaIkaE=; b=xnCwacws2OZc0IhDoVd6PkpgfPVJad2zMJxy3gW1qo0F/E4O6yX81C+qcdCScql62Q cHcTaWBuneU1BTWiFSkv2ZHxScVHwvZXoUxpnthg9UHGugzjHR2WsYfIOzn8HqaNS9s7 VMNCP8nbaM7A/klXf7iPliWG12dN/0hIapNIIkNX/Q8LV0C4xGiWvN8esRHG3x/9nvWE RcMeD1V7pY/QZIt7QEDMjJjB3eijcjeRwPxeGRa+AWdC1xajERyP92nyaNzyKW7HvfJ7 14y627hERD35sLFM96SjToJKOXrbXkakEYnFtXF/JtGfQdjXcN3ktvubaXYz0dqutTNa ARC-Authentication-Results: i=2; mx.google.com; spf=pass (google.com: domain of magfr@lysator.liu.se designates 130.236.254.3 as permitted sender) smtp.mailfrom=magfr@lysator.liu.se DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:subject:message-id:mail-followup-to:references :mime-version:content-disposition:in-reply-to:user-agent :x-original-sender:x-original-authentication-results:reply-to :precedence:mailing-list:list-id:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=ubNU1M9CizZO6oRO0onstl0qa8tILrqRkgXaJwaIkaE=; b=US0u06sNDaq0NjhlIjYEbHbWq6vTbEy8MIa6WojLe/M2IaY9SafqXR0gLc71bxwYlF /wqWrfF3BtdWz0y/ErZv7Qb3iJoXr+AlCuTDrJ75WVpO5/N0QJEjEbrafy6/AJMAajuB qDxjH0LR4VjvpbsFubuxZF1Cx5gpqB80wjo1BoS6dYyvFkIiz6mlF0iPt7ul6zmuqGPp w383id091u1BRk4dEREPT2aNKTa4KhJiaGjDFAAQJo5BhF2itnmr6wfTnPQAcqMuAXFK 211XGnitbQpDI+JxoUgyedwDHCc6kHUg5ynGekRN5ewqEQFKXqnIst4x5fnDMpQrySSu y6kg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:subject:message-id:mail-followup-to :references:mime-version:content-disposition:in-reply-to:user-agent :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=ubNU1M9CizZO6oRO0onstl0qa8tILrqRkgXaJwaIkaE=; b=MXNqIDY0+f4itwC0tnb9oKjZvHZ4ljewyoZ9ZI2AoHZ6P0cNFVzomWLppuNxoaQPgN hEFVysmlc4zrZ/deIcrFVR2lGQiuvh3qnF556iHI/H0yPLfxXBgdrIyY8BINSsTVWW9g 0OpjppGHsFVdqCkPiMVLm4kY0G1A+nfmURP7ICE7QKi3r1HxbAi8S3ZjsI+fTh4+AhNa FrzAsD2uD4xjvQuY7qLsiR52jdfUVT0K7IohCDqhPfqVXDu6GBHAe6iJkL8UrDAL6jaq FEIRgEf7M/dhJb9gWJcVTCZhMxzeMtHfqNC+D9jWSbMLhBIylX86fgUHfXV X-Gm-Message-State: AElRT7FlX6JuZDPn+YONh+L/SIR8O5+6EXAerZSoWIK3avCKtUfTK0Ma +nJ3B9Fn7J4bd0A39JLVMgRkNA== X-Google-Smtp-Source: AIpwx48EUxf28hqDXfGHQwa/muqAeQQQvze5GJirKoogDmR3K/TevhCbHvHoWLMreAS03CLzdwtlxQ== X-Received: by 10.46.137.2 with SMTP id d2mr1628648lji.44.1522388881057; Thu, 29 Mar 2018 22:48:01 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.46.33.211 with SMTP id h80ls941838lji.13.gmail; Thu, 29 Mar 2018 22:47:59 -0700 (PDT) X-Received: by 10.46.29.140 with SMTP id w12mr7099289lje.108.1522388879422; Thu, 29 Mar 2018 22:47:59 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1522388879; cv=none; d=google.com; s=arc-20160816; b=nZixvbu5TIMxe+FJcdlDZRugxHqe6Y9YMcDsue4nIF1iMRR3fFgF36rsuOsqd51s5V rL7C2/NTv6BfXJkHMuvCHMlDXHVhFhPrtQqxLezHE7qM/etAmCOlb1ruPBZrH5EZaOd1 TUMRwmXkjImMdVP3K/jCi90o2D3EtEmVBFkxnZYVqJsT4R3vVGdpslmn2RTgkWHjyU9O 1cs8Fa3Ehr88ETWSC4ZdU5ZMbRePSVjPUImWv476wc/XfzRqN29J1iXPemtgz46DmIhK X31h6Ns+GCfjyWHXsWQieWyZjn3gl0S9FUe0bTpYF/bAUvptnKgXFCR4wHT5FfgumQQP Uf6w== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=user-agent:in-reply-to:content-disposition:mime-version:references :mail-followup-to:message-id:subject:to:from:date :arc-authentication-results; bh=aHO63jTcQ1laYPMq2AXuYRBcg07fvYAIe1t9VcL+pYk=; b=TdZzWNDVJthJjLL0LQjke2UYljl8t3fKFa/F7SFSlMQHZ++DC8hH+fpgWqvXm6EB9u w427YOEibj9IV4wILhX/E7J4UoLX0Vw++uwMBnxvpeOR2MOB41vVqoxB6mQYuUcqf4gg LqZfSqYlRIibuYH4OHlvkO68nH198oCwmLzhw+/y0+fJaWnFBbr0/g2/JfIWEk3PTjsC m5+SqpcijthGcjOmxLdfVG/48OXQPffexRJvppCHUhS/it/FGck8t4HmhJvyv+T/M/EY wTq6wKv5KioDKZm1YWmjFlDjD9BBBcF6tsmpoAo16emEuyk7R7Tezfrir8xXAA/5gQje k3oA== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of magfr@lysator.liu.se designates 130.236.254.3 as permitted sender) smtp.mailfrom=magfr@lysator.liu.se Original-Received: from mail.lysator.liu.se (mail.lysator.liu.se. [130.236.254.3]) by mx.google.com with ESMTPS id z10-v6si2893838lfj.196.2018.03.29.22.47.59 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 29 Mar 2018 22:47:59 -0700 (PDT) Received-SPF: pass (google.com: domain of magfr@lysator.liu.se designates 130.236.254.3 as permitted sender) client-ip=130.236.254.3; Original-Received: from mail.lysator.liu.se (localhost [127.0.0.1]) by mail.lysator.liu.se (Postfix) with ESMTP id D3B144001E for ; Fri, 30 Mar 2018 07:47:58 +0200 (CEST) Original-Received: from noemi (user172.77-105-211.netatonce.net [77.105.211.172]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.lysator.liu.se (Postfix) with ESMTPSA id B06AA4000D for ; Fri, 30 Mar 2018 07:47:58 +0200 (CEST) Mail-Followup-To: std-proposals@isocpp.org Content-Disposition: inline In-Reply-To: <5e47cc81-4834-4a68-8925-717fb2ec8612@isocpp.org> X-Virus-Scanned: ClamAV using ClamSMTP X-Original-Sender: magfr@lysator.liu.se X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of magfr@lysator.liu.se designates 130.236.254.3 as permitted sender) smtp.mailfrom=magfr@lysator.liu.se 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:37567 Archived-At: On Thu, Mar 29, 2018 at 07:01:03PM -0700, liweifriends@gmail.com wrote: > > For a program that heavily depends on compile time calculation, this might > be a serious problem, since the compiler might store a lot of such > "useless" information during compile, this will increase the memory useage > of the compiler and slow down the compile procedure. > > To solve this problem, I think we should introduce an "metafunction" scope, > as follows: > > metafunction > { > template > struct RemoveConstReference > { > using tmp = typename std::remove_const::type; > using type = typename std::remove_reference::type; > }; > } > > using ResType = typename RemoveConstReference::type; Your example does not make any sense. Ain't RemoveConstReference out of scope at the point of "using ResType"? > the RemoveConstReference is included inside this scope, so after the > calculation of ResType, the compiler might remove all the information > generated inside this scope. This will save the memory of the compiler and > speed up the compile procedure. If, on the other hand you put "using ResType" before the closing brace of the metafunction clause then ResType would become undefined right after it's definition and that also is unusable. As a final thoght this sounds a lot like a namespace with an unutterable name, how does your metafunction compare to a namespace? /MF -- 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. To view this discussion on the web visit https://groups.google.com/a/isocpp.org/d/msgid/std-proposals/20180330054757.GA2396%40noemi. .