220 26534 article Path: news.gmane.org!not-for-mail From: Ville Voutilainen Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Adding a const qualifier to class access modifiers Date: Mon, 4 Jul 2016 12:52:41 +0300 Lines: 59 Approved: news@gmane.org Message-ID: References: <7145a8aa-6a74-4ff3-8984-4a74aef66b5d@isocpp.org> <20160704042756.GA19918@noemi> 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 1467625966 15470 80.91.229.3 (4 Jul 2016 09:52:46 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Mon, 4 Jul 2016 09:52:46 +0000 (UTC) To: "ISO C++ Standard - Future Proposals" Original-X-From: std-proposals+bncBC5JHI7A7ALRB2XD5C5QKGQENRERKVA@isocpp.org Mon Jul 04 11:52:46 2016 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-vk0-f69.google.com ([209.85.213.69]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1bK0YX-0001Au-3Q for gclcip-std-proposals@m.gmane.org; Mon, 04 Jul 2016 11:52:45 +0200 Original-Received: by mail-vk0-f69.google.com with SMTP id v6sf440144928vkb.2 for ; Mon, 04 Jul 2016 02:52:44 -0700 (PDT) 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:from:date:message-id:subject:to :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=jrJg/iASmF75UQWVt3Yd4Te8HUskPG7byiZKF+EEIQU=; b=rcU0AxvRby4/pgndcyvlknNvHdSs41aio9MWZyPrI3oVFddV6w3iEQBbwFdf5QXMyj 28x2/u7YmmJwXTLidytw7L91BqkopMzEuBdwM942cflQe+wV81lreesF8VJpPRsrqovf 8uKjKfV7kggnqYKUGt/v7++rk1YmJSZTK6NRtdI66Bo/c6QumICHDqwBHMjdy04b5JYo O0NnMFIO7T7FLfh4C1y7aZyXDWmOUimflitxcdRvhurJifa+aeSBuBIf5qqyuMFfQ6xe Zk/vsOARuMWJIbRcTatINvmNLKpWH/RgiaUzYvDhWS3awK9imIxIuTr5Hm+LZGDPRWCq J9Lw== 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:from:date :message-id:subject:to: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=jrJg/iASmF75UQWVt3Yd4Te8HUskPG7byiZKF+EEIQU=; b=DDsDzecApkBv3msvxiYgXwzKcK0ObRDCWTDCEFm0VOny85iMBmpwYE/ATVB/DkEKhg 7M5J+ESF+dpP8GdoSkBcQcFrvZwOfs9vd9jpdWNhoH6AxLlHba2IQLIMN7z6DeE3as5M fjqfnnhVLtnrdw7DNMK9cmAO78n64mjgNxPtKWkIf9EH57QrM6SSxoB54+50EAG9D3rG J1XLeUia7vcvCeUdPEe2sZbkqjmYg50Q4joQTpxPoxYSitIhcyDURBEw4urKBfgh45fs Amgcyh849yqgmtjD0sbeIvU8ApHvpR1nfV3GDYZKb3WskwWVSLeSg/5yE9kIZYgjoSdB YP2 X-Gm-Message-State: ALyK8tKgI1Sae0uF4XDL5P5SthLdjBwlfaT+N+Ns/jODRH+N/xrltWdNMWODYt4e6J2O5A== X-Received: by 10.200.42.242 with SMTP id c47mr29743818qta.22.1467625963786; Mon, 04 Jul 2016 02:52:43 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.107.32.209 with SMTP id g200ls1395103iog.65.gmail; Mon, 04 Jul 2016 02:52:42 -0700 (PDT) X-Received: by 10.176.4.49 with SMTP id 46mr3824945uav.32.1467625962364; Mon, 04 Jul 2016 02:52:42 -0700 (PDT) Original-Received: from mail-vk0-x22c.google.com (mail-vk0-x22c.google.com. [2607:f8b0:400c:c05::22c]) by mx.google.com with ESMTPS id f97si920842vki.88.2016.07.04.02.52.42 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 04 Jul 2016 02:52:42 -0700 (PDT) Received-SPF: pass (google.com: domain of ville.voutilainen@gmail.com designates 2607:f8b0:400c:c05::22c as permitted sender) client-ip=2607:f8b0:400c:c05::22c; Original-Received: by mail-vk0-x22c.google.com with SMTP id i63so55516569vkb.2 for ; Mon, 04 Jul 2016 02:52:42 -0700 (PDT) X-Received: by 10.176.66.98 with SMTP id i89mr3816295uai.149.1467625961983; Mon, 04 Jul 2016 02:52:41 -0700 (PDT) Original-Received: by 10.103.64.83 with HTTP; Mon, 4 Jul 2016 02:52:41 -0700 (PDT) In-Reply-To: <20160704042756.GA19918@noemi> X-Original-Sender: ville.voutilainen@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com; spf=pass (google.com: domain of ville.voutilainen@gmail.com designates 2607:f8b0:400c:c05::22c as permitted sender) smtp.mailfrom=ville.voutilainen@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:26534 Archived-At: On 4 July 2016 at 07:27, Magnus Fromreide wrote: > On Sun, Jul 03, 2016 at 06:25:42PM -0700, =C3=93lafur Waage wrote: >> One of the biggest things I have seen in developing medium to large scal= e >> systems is how useful const is to show the original author's intent, tha= t >> this value should not be changed, even by grabbing a mutable variable an= d >> creating a const auto& temporary and using that temporary to state that >> this value should stay the same. >> >> This get's tricky when dealing with class members, especially when >> accessing them from the outside. >> >> Should you limit access via private and provide a Get function? >> - Writing all those Get type functions can get tiring and bloats the cla= ss >> with very trivial functions, even if they return a copy or a const ref. >> >> Should you keep it public and take the python stance of "we're all adult= s >> here"? >> - Opening the access to anyone outside can later down the line introduce >> errors if it's a value that needs to be updated in a certain way to keep >> the internal state of the class sane. > > The usual reply to this question is neither. > > What you should do is move the logic that need to access the value into > methods of the class so that the class becomes more self contained. > Yes, I am aware of this beeing harder to but the resulting system is gene= rally > easier to understand since there is less coupling between different class= es. With NDSMIs, this is what I'd do: class X { string data; public: const string& cdata =3D data; }; I don't think the suggested problem is so common that we need to invent a new kind of an access specifier to cater 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/CAFk2RUaAW%2BxPzW5ov85qD0m9Dv6nikHZd0asUG7%3D2ri= nv3navg%40mail.gmail.com. .