220 26537 article Path: news.gmane.org!not-for-mail From: Matthew Woehlke Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Adding a const qualifier to class access modifiers Date: Mon, 04 Jul 2016 10:50:30 -0400 Lines: 68 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 1467643854 5595 80.91.229.3 (4 Jul 2016 14:50:54 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Mon, 4 Jul 2016 14:50:54 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBC37LBFWUIFBBQ7P5G5QKGQE6LLWU4Q@isocpp.org Mon Jul 04 16:50:45 2016 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-wm0-f69.google.com ([74.125.82.69]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1bK5Cv-0005jy-Bb for gclcip-std-proposals@m.gmane.org; Mon, 04 Jul 2016 16:50:45 +0200 Original-Received: by mail-wm0-f69.google.com with SMTP id a66sf68723121wme.1 for ; Mon, 04 Jul 2016 07:50:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=to:from:subject:date:lines:message-id:references:mime-version :content-transfer-encoding:user-agent:in-reply-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=oQeQ/uLEHmaQYbUVgxZN2LraeqLLXDKHtVnDkPRULlM=; b=rIoooOGtuslNKnAeDZDvPgaKB/3oiMZax+a4b85d+Pt9KNMh3KTC2hiZmu1s468AEj vX63JQXWp2YLNQTk5Ikj5ce7GYzoWHi/7Bp7h0mhHpE6j1kgDHIr+ptjnene8G5HnzZc 3hyVVS12wUk4TCoGrhgDDvenrBQoJv+shbkW85ElZaIhYIT20U4GmE/h5BwIhSsVzcJV x06g7BSiwfDcwy/DE9hUT2udpmVwQ1pzvUVPQHflQ6xTLl12EU6B7UScECtvbIjGSnL0 TSigR5+2OZ1VAoz5kPySPpmSYAuWmchY1u99d4GjAkOJe3BokqaGXn5mbg2h7S7LcESs X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:to:from:subject:date:lines:message-id:references :mime-version:content-transfer-encoding:user-agent:in-reply-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=oQeQ/uLEHmaQYbUVgxZN2LraeqLLXDKHtVnDkPRULlM=; b=Xbz6zscHsdJVsMMwdl2cWS1sKIR5EIhbPPoIUUjV42X+M6sX/x3yPFwClT1bES1qhH ikR5+notojcwiucPAPrA1WdNzfmjSWWOb6mf8JACitUal3mcxu64YtRmOJNJ2LlGuFYC IxZOfKOKhVtk6Cj4rkLhLB6D3o7jhElbHDAL3/OM5w5lGh92V+Tk5d1RHsiiqgTZ/hNf IfH2VAx25hhWJVVAslOkGxr3l8x5MpHWlliUB05lB6HbZYd9A5YLdytuyzh8xFhAcnGz plVxdsmxIrK+H6nzZUcYQyBMPva81K1cDqAYXwFfd695ehMsEHGhrBy2PQ2PnvNS X-Gm-Message-State: ALyK8tKZAzCnvO5V0f4y8n3zGpMjhFn6ltTbwQHMnJfEU6PhoVSGisQx4AH1bg8A+SUBYQ== X-Received: by 10.28.197.196 with SMTP id v187mr1846992wmf.3.1467643844684; Mon, 04 Jul 2016 07:50:44 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.46.33.74 with SMTP id h71ls150757ljh.45.gmail; Mon, 04 Jul 2016 07:50:43 -0700 (PDT) X-Received: by 10.25.168.202 with SMTP id r193mr3728695lfe.85.1467643843050; Mon, 04 Jul 2016 07:50:43 -0700 (PDT) Original-Received: from plane.gmane.org (plane.gmane.org. [80.91.229.3]) by mx.google.com with ESMTPS id u143si2095846lff.104.2016.07.04.07.50.42 for (version=TLS1 cipher=AES128-SHA bits=128/128); Mon, 04 Jul 2016 07:50:42 -0700 (PDT) Received-SPF: pass (google.com: domain of gclcip-std-proposals@m.gmane.org designates 80.91.229.3 as permitted sender) client-ip=80.91.229.3; Original-Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1bK5Co-0005gQ-Q2 for std-proposals@isocpp.org; Mon, 04 Jul 2016 16:50:39 +0200 Original-Received: from tripoint.kitware.com ([66.194.253.20]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Mon, 04 Jul 2016 16:50:38 +0200 Original-Received: from mwoehlke.floss by tripoint.kitware.com with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Mon, 04 Jul 2016 16:50:38 +0200 X-Injected-Via-Gmane: http://gmane.org/ Original-Lines: 49 Original-X-Complaints-To: usenet@ger.gmane.org X-Gmane-NNTP-Posting-Host: tripoint.kitware.com User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 In-Reply-To: X-Original-Sender: mwoehlke.floss@gmail.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of gclcip-std-proposals@m.gmane.org designates 80.91.229.3 as permitted sender) smtp.mailfrom=gclcip-std-proposals@m.gmane.org; dmarc=fail (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:26537 Archived-At: On 2016-07-04 05:52, Ville Voutilainen wrote: > 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 sca= le >>> systems is how useful const is to show the original author's intent, th= at >>> this value should not be changed, even by grabbing a mutable variable a= nd >>> 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 cl= ass >>> 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 adul= ts >>> here"? >>> - Opening the access to anyone outside can later down the line introduc= e >>> errors if it's a value that needs to be updated in a certain way to kee= p >>> 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 gen= erally >> easier to understand since there is less coupling between different clas= ses. >=20 > With NDSMIs, this is what I'd do: >=20 > class X > { > string data; > public: > const string& cdata =3D data; > }; >=20 > 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. Actually, properties would be great here; provide a public get but no set. The problem with the above is that it increases the size of the class. The most recent iteration of "properties", involving inner classes and zero-size members, would solve this. --=20 Matthew --=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/nldt3m%24onh%241%40ger.gmane.org. .