220 22822 <91a92c5c-60fe-4d94-b831-cd940cd3e56a@isocpp.org> article Path: news.gmane.org!not-for-mail From: Nicol Bolas Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: interface constraints for a template Date: Sun, 22 Nov 2015 07:56:32 -0800 (PST) Lines: 82 Approved: news@gmane.org Message-ID: <91a92c5c-60fe-4d94-b831-cd940cd3e56a@isocpp.org> References: <58bd5a73-1b31-45cf-8141-eb01093417ea@isocpp.org> <48aa536a-b112-4f40-96cc-7625e233d244@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_53_1034410841.1448207792197" X-Trace: ger.gmane.org 1448207800 28918 80.91.229.3 (22 Nov 2015 15:56:40 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Sun, 22 Nov 2015 15:56:40 +0000 (UTC) Cc: sergeikrivonos@gmail.com To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCEKFTV6ZUMBBMOLY6ZAKGQEWFB7QXQ@isocpp.org Sun Nov 22 16:56:36 2015 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-pa0-f71.google.com ([209.85.220.71]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1a0X0E-0006Ze-Nz for gclcip-std-proposals@m.gmane.org; Sun, 22 Nov 2015 16:56:34 +0100 Original-Received: by pacej9 with SMTP id ej9sf5208086pac.0 for ; Sun, 22 Nov 2015 07:56:34 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:message-id:in-reply-to:references:subject :mime-version:content-type:x-original-sender:reply-to:precedence :mailing-list:list-id:x-spam-checked-in-group:list-post:list-help :list-archive:list-subscribe:list-unsubscribe; bh=XiJPbgCoLKSUcskFJY36kzfKAFMtzKRXv7kx8fP3Wh4=; b=lfV5HlD444pmGy+uGq3cqymTIVqF7aPMeodcobhv8rT/a1l5OSjwCG3EhCjXQul2C6 FW+IUdU6BjQLDbt/LvwrGmqk1ckceWgORgwnrfA+02fyT8VzI847A2hF81LhDWopHrJB 2bkXmDj+dCt+SrPAumqHK/beCeyho+JhzA7Lyi4ckuNPeLVyDcofw8MSRSaHRJEZQA95 cSi3iDpZI1h0ZPvn5NoDMDita+LEZGKTkOheUHuc4tT2WBdCC8WAu4TphJEQYRArwIPN xjeL7O4MmLZlpIw+XEht+EoxQltUZ+5MoJTAWGaItHesuYuBUpocxW/8w2dsG8WrTCCz +QUQ== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=date:from:to:cc:message-id:in-reply-to:references:subject :mime-version:content-type:x-original-sender:reply-to:precedence :mailing-list:list-id:x-spam-checked-in-group:list-post:list-help :list-archive:list-subscribe:list-unsubscribe; bh=XiJPbgCoLKSUcskFJY36kzfKAFMtzKRXv7kx8fP3Wh4=; b=uXbb1CLLa3wHVWaYD2AFCpYcB3LRO6fLiNSxLZaubs8kH4JidO+dDb7VOaSVq9K4/k ejQxcR3/m55sxydmCIXv6LKrVqCbToFKzOKO7/KC6fiDoBTN61ymWwFPV0gNY9oczF0F fxrCjo0uK3OlumbS6nLTjjrIB+QIqJX0Lv4xfeGLhfF4mp9/I2OoYQ0daLxZCeKJoQqu YWBUe2vE1CUFKmmQ2R7YUNkSOLwVnHlvQYk6i66NFpq86VTuguhN3fnVOxiugFwUJ2xc 57zLS+h9jUNVhoVX5MbulyiVMTO+GdhMqON6aZuQ1oZ1n0/Vf1bttaclhKQANt/U+ilj e9KQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:date:from:to:cc:message-id:in-reply-to :references:subject:mime-version:content-type:x-original-sender :reply-to:precedence:mailing-list:list-id:x-spam-checked-in-group :list-post:list-help:list-archive:list-subscribe:list-unsubscribe; bh=XiJPbgCoLKSUcskFJY36kzfKAFMtzKRXv7kx8fP3Wh4=; b=lN5DAyVbn1uWwZTTm87zu+IGKkO69Kt5TBpB3jLUfy4Z9UpuJ2PXg3/0/g05O8mRSP 4InA88k4vYzQB9E4DNb63UkgzcJ+SItUPFcBr5wmGdsYP1t0eqn9IV/R+AUHSntIRGkX xMsfIAXLp5fFMeTUX+MJs++nyB39sneEYSSavRzXqBhhqBVfHLAxdfBV26ZwW/5WtqQc VfXXJYqdAlYKxOhXP6UOHcKQYcyk/i7/N8833Eax3vcwaLzIIXZ8fGiSGAMryYWFi3hx Gv4we73bDNZRej/xalYOchW5DvD2DjhDHTHS9r62UIofGRHtT8kKIqBHRJ4dJYbgXs6Y rhVA== X-Gm-Message-State: ALoCoQnuLCYP/PD+BdsITOPJip5loHRXMiMn89+yvB3IArLTV+ZvnDMWWrV1cPvH0qASMp8EKxQX X-Received: by 10.66.124.196 with SMTP id mk4mr20549307pab.23.1448207793985; Sun, 22 Nov 2015 07:56:33 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.107.128.94 with SMTP id b91ls1297677iod.95.gmail; Sun, 22 Nov 2015 07:56:33 -0800 (PST) X-Received: by 10.50.20.162 with SMTP id o2mr235563ige.7.1448207793278; Sun, 22 Nov 2015 07:56:33 -0800 (PST) In-Reply-To: <48aa536a-b112-4f40-96cc-7625e233d244@isocpp.org> X-Original-Sender: jmckesson@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:22822 Archived-At: ------=_Part_53_1034410841.1448207792197 Content-Type: multipart/alternative; boundary="----=_Part_54_704085495.1448207792197" ------=_Part_54_704085495.1448207792197 Content-Type: text/plain; charset=UTF-8 On Sunday, November 22, 2015 at 10:55:28 AM UTC-5, Nicol Bolas wrote: > > We call those `concepts > `. > > However, I think it's silly to constrain a function based on a base class. > Constrain it based on the *interface* provided by that base class. Why > does it matter if the user derived from that class or not? What matters is > whether the class they provide offers the proper interface? > > If you wanted to constrain the parameter on a base class, you should take > the base class itself as a parameter and not use a template parameter at > all. > Not to mention, you're using a *virtual function*. The whole point of that is that you can call it from a base class pointer and get a call to the method in the derived class. Using template polymorphism on top of virtual polymorphism makes no sense. -- --- 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. Visit this group at http://groups.google.com/a/isocpp.org/group/std-proposals/. ------=_Part_54_704085495.1448207792197 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable

On Sunday, November 22, 2015 at 10:55:28 AM UTC-5, Nicol Bolas wrot= e: