220 12976 article Path: news.gmane.org!not-for-mail From: Tony V E Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Idea for new contextual keyword Date: Thu, 18 Sep 2014 11:12:42 -0400 Lines: 86 Approved: news@gmane.org Message-ID: References: <2ff42d9d-16df-4040-8ae1-0a17d4f78d97@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary=089e0158ad547cc9aa0503586a7a X-Trace: ger.gmane.org 1411053172 31308 80.91.229.3 (18 Sep 2014 15:12:52 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Thu, 18 Sep 2014 15:12:52 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCUZ5QWKNQIOX3HLUACRUBATVMNOO@isocpp.org Thu Sep 18 17:12:45 2014 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-ee0-f71.google.com ([74.125.83.71]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1XUdO0-0006UI-RW for gclcip-std-proposals@m.gmane.org; Thu, 18 Sep 2014 17:12:44 +0200 Original-Received: by mail-ee0-f71.google.com with SMTP id e53sf748323eek.10 for ; Thu, 18 Sep 2014 08:12:44 -0700 (PDT) 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:x-original-sender :x-original-authentication-results:reply-to:precedence:mailing-list :list-id:list-post:list-help:list-archive:list-subscribe :list-unsubscribe:content-type; bh=UlOI2tyw68nrgVc81gSYpTK5MlzZGIKm6otqNS6ghHI=; b=NN18+c8YIRc5JAUgEMiXSFyE8JARB7b61pqRf7bm1DHFXeadzMf7SrGVW/NDAPXyEO YH7JW29C9u7T389daNMQ6o5NPsgFiGydupiFIr5YI/tWAdJJEc4WeCgo1ypVG5g3lkxL T37GXbTv0Yr+eRz61ONeRWkHyasECTV7ipzM/GJXBkHjgbbWzaQmOnne2ZHfJ1VqyGCN 9CxpyyF7aM/JjkS3SB/CqR+hgYFDvRucioHZhPPKBEouhaRFfMQIRU4BbdVnO0+NeNi0 4/uoAFCI0Ou7nE8wXt/79Pknl7TN3bXq1avlHdLWU/zuKMt41g0wEqt2ndltXp4O09+T 8Z9Q== X-Gm-Message-State: ALoCoQm/9tP901HnnvIfRN/rzmqr1eRV/s2zs9aixl0LNgNxEiiq9poTAy21WMobYkvg59pBKDEI X-Received: by 10.112.190.102 with SMTP id gp6mr625486lbc.10.1411053164412; Thu, 18 Sep 2014 08:12:44 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.152.246.35 with SMTP id xt3ls214089lac.67.gmail; Thu, 18 Sep 2014 08:12:42 -0700 (PDT) X-Received: by 10.152.170.167 with SMTP id an7mr366408lac.94.1411053162567; Thu, 18 Sep 2014 08:12:42 -0700 (PDT) Original-Received: from mail-lb0-x22e.google.com (mail-lb0-x22e.google.com [2a00:1450:4010:c04::22e]) by mx.google.com with ESMTPS id qi3si33255624lbb.41.2014.09.18.08.12.42 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Thu, 18 Sep 2014 08:12:42 -0700 (PDT) Received-SPF: pass (google.com: domain of tvaneerd@gmail.com designates 2a00:1450:4010:c04::22e as permitted sender) client-ip=2a00:1450:4010:c04::22e; Original-Received: by mail-lb0-f174.google.com with SMTP id l4so1361818lbv.33 for ; Thu, 18 Sep 2014 08:12:42 -0700 (PDT) X-Received: by 10.152.21.168 with SMTP id w8mr245024lae.59.1411053162120; Thu, 18 Sep 2014 08:12:42 -0700 (PDT) Original-Received: by 10.112.75.199 with HTTP; Thu, 18 Sep 2014 08:12:42 -0700 (PDT) In-Reply-To: <2ff42d9d-16df-4040-8ae1-0a17d4f78d97@isocpp.org> X-Original-Sender: tvaneerd@gmail.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of tvaneerd@gmail.com designates 2a00:1450:4010:c04::22e as permitted sender) smtp.mail=tvaneerd@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-Google-Group-Id: 399137483710 List-Post: , List-Help: , List-Archive: List-Subscribe: , List-Unsubscribe: , Xref: news.gmane.org gmane.comp.lang.c++.isocpp.proposals:12976 Archived-At: --089e0158ad547cc9aa0503586a7a Content-Type: text/plain; charset=UTF-8 On Wed, Sep 17, 2014 at 7:27 PM, Leor Zolman wrote: > Hi all, > This is my first-ever attempt at initiating a proposal; I look forward to > the process. > > I think there's gaping hole in C++ that permits (or, more importantly, > prevents the class designer from prohibiting) the redefinition/hiding of a > non-virtual function. As Scott Meyers says in items 35 and 36 of *Effective > C++ (3rd Ed.)*, non-virtual functions are supposed to represent *invariants > over specialization*. Yet, C++ currently offers no mechanism whereby a > function can be flagged explicitly as "not to be redefined." > > Following some great conversations at CppCon (the most illuminating being > one I had with stl), I'd like to propose a new contextual keyword that > would be closely related to final/override (and written similarly.) The > best name I've been able to think of so far for this new keyword is > "invariant." > > Since 'final' only applies to virtual functions, 'invariant' would only be > applicable to non-virtual functions, and make it an error to redefine the > function in a derived class. > Why not just reuse 'final' then? Tony -- --- You received this message because you are subscribed to the Google Groups "ISO C++ Standard - Future Proposals" group. 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On Wed, Sep 17, 2014 at 7:27 PM, Leor Zolman <leorzolman@gmail.com<= /a>> wrote:
Hi= all,
This is my first-ever attempt at initiating a proposal; I look for= ward to the process.

I think there's gaping hole in C++ that per= mits (or, more importantly, prevents the class designer from prohibiting) t= he redefinition/hiding of a non-virtual=C2=A0 function. As Scott Meyers say= s in items 35 and 36 of Effective C++ (3rd Ed.), non-virtual functio= ns are supposed to represent invariants over specialization. Yet, C+= + currently offers no mechanism whereby a function can be flagged explicitl= y as "not to be redefined."

Following some great conversa= tions at CppCon (the most illuminating=20 being one I had with stl), I'd like to propose a new contextual keyword= that=20 would be closely related to final/override (and written similarly.) The bes= t name I've been able to think of so far for this new keyword is "= invariant."

Since 'final' only applies to virtual funct= ions, 'invariant' would only be applicable to non-virtual functions= , and make it an error to redefine the function in a derived class.


Why not just reuse 'final' = then?

Tony



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