220 16815 <54F9ED4C.2030108@stroustrup.com> article Path: news.gmane.org!not-for-mail From: Bjarne Stroustrup Newsgroups: gmane.comp.lang.c++.isocpp.proposals,gmane.comp.lang.c++.isocpp.general Subject: Re: [c++std-core-27226] Re: An implementation of enhanced auto deduction and abbreviated template syntax using Clang Date: Fri, 06 Mar 2015 13:09:16 -0500 Lines: 161 Approved: news@gmane.org Message-ID: <54F9ED4C.2030108@stroustrup.com> References: <465969eb-2f8b-41bb-91af-d8a9e22985e7@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="------------040700010608050100060009" X-Trace: ger.gmane.org 1425665366 29981 80.91.229.3 (6 Mar 2015 18:09:26 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Fri, 6 Mar 2015 18:09:26 +0000 (UTC) Cc: std-proposals@isocpp.org, faisalv@gmail.com, hsutter@microsoft.com To: c++std-core@accu.org, std-discussion@isocpp.org Original-X-From: std-proposals+bncBDDP5YUK74KBBTW246TQKGQEA343CTQ@isocpp.org Fri Mar 06 19:09:20 2015 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-pd0-f200.google.com ([209.85.192.200]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1YTwgZ-0002EC-SD for gclcip-std-proposals@m.gmane.org; Fri, 06 Mar 2015 19:09:20 +0100 Original-Received: by pdev10 with SMTP id v10sf84310213pde.0 for ; Fri, 06 Mar 2015 10:09:19 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:message-id:date:from:user-agent:mime-version:to :cc:subject:references:in-reply-to:content-type: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=ncsj4mVxrs5o2n5zZiTmi/Hb7fNb0YH8HJs/cPb3zEA=; b=d7S2eftonbqSeCHGt5aG6EdAheWJgdkzgvdUZhstlPU7kyBCb6gtx/xAG1Ae5E7B65 jes9mDpp3GJzcpOIfxp/UV80Gm80LTQKYQcL+Q2TvDDDNyg7hkuaSnJFsUthZu2EmVvY Q9TKtbzf28riHvC8w/l27CGGVFjmfxnaULMhLDPEcke9xhrnIf+agCt6aVYQzQPt/bfO qGgPprvEX8j/tTkMzRhm+JQy+vL6Dy4rOliHEgIlhnq4PkDtvEOTepeLahk8BiQ5d5aQ 6MH+Z8sVDN9iPDqC4vMigfEYsS0O22sjTlbGir3wI5l0PETVI2vxlw0+m/0GNKqFIA6Y Dzzw== X-Gm-Message-State: ALoCoQlFcF7kbu1/ItAmdOhcbMa/DJ681qb+EXmPqWzAVHSroLNCpG55CvDKjbe31Cu8mKqQrxD2 X-Received: by 10.70.96.163 with SMTP id dt3mr10664093pdb.1.1425665358988; Fri, 06 Mar 2015 10:09:18 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.140.109.119 with SMTP id k110ls384999qgf.56.gmail; Fri, 06 Mar 2015 10:09:18 -0800 (PST) X-Received: by 10.55.22.32 with SMTP id g32mr26482817qkh.4.1425665358100; Fri, 06 Mar 2015 10:09:18 -0800 (PST) Original-Received: from mail-qg0-f48.google.com (mail-qg0-f48.google.com. [209.85.192.48]) by mx.google.com with ESMTPS id s30si10012159qge.45.2015.03.06.10.09.18 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 06 Mar 2015 10:09:18 -0800 (PST) Received-SPF: none (google.com: bjarne@stroustrup.com does not designate permitted sender hosts) client-ip=209.85.192.48; Original-Received: by qgdz107 with SMTP id z107so14513652qgd.3 for ; Fri, 06 Mar 2015 10:09:18 -0800 (PST) X-Received: by 10.140.151.13 with SMTP id 13mr21544118qhx.68.1425665357952; Fri, 06 Mar 2015 10:09:17 -0800 (PST) Original-Received: from ?IPv6:2001:18d8:ffff:16:7457:3844:86b:f063? ([2001:18d8:ffff:16:7457:3844:86b:f063]) by mx.google.com with ESMTPSA id 201sm6220607qhd.11.2015.03.06.10.09.16 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 06 Mar 2015 10:09:16 -0800 (PST) User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0 In-Reply-To: <465969eb-2f8b-41bb-91af-d8a9e22985e7@isocpp.org> X-Original-Sender: bjarne@stroustrup.com X-Original-Authentication-Results: mx.google.com; spf=none (google.com: bjarne@stroustrup.com does not designate permitted sender hosts) smtp.mail=bjarne@stroustrup.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:16815 gmane.comp.lang.c++.isocpp.general:5019 Archived-At: This is a multi-part message in MIME format. --------------040700010608050100060009 Content-Type: text/plain; charset=UTF-8; format=flowed On 3/6/2015 1:07 PM, Nicol Bolas wrote: > > > On Friday, March 6, 2015 at 12:38:14 PM UTC-5, Jonathan Wakely wrote: > > On 6 March 2015 at 17:21, Nicol Bolas wrote: > > Explain to me, the novice C++ programmer, why this thing which > doesn't look > > like a template suddenly became a template. Explain to me why I > have to > > implement it in a header, even though it looks exactly like > every other > > non-template function declaration/definition. > > > > To the novice C++ programmer, it isn't "all just programming." > Whether > > something is a template matters. > > Ah, the "won't somebody think of the children" argument. > > The answer to why it suddenly became a template is that its parameter > is a concept, not a type. A concept is a family of types. I don't > see > why that should be much harder to teach than "a function template > is a > family of functions" and "a class template is a family of types". > > > If a "family of functions" is so fundamentally different from a > regular function that it can't be declared/defined in the same way, > why does it look exactly like a regular function? If swapping one > identifier for another can so radically change how you go about > implementing something, shouldn't it be more syntactically obvious > that you've made a major change? > > Without the template keyword, it doesn't look like a template. And > therefore, it is not immediately obvious that it should be treated as > such. > People will learn. Learning that void f(auto); implies template is kid's play compared to some things we expect people to figure out. -- --- 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/. --------------040700010608050100060009 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable

On 3/6/2015 1:07 PM, Nicol Bolas wrote:<= br>


On Friday, March 6, 2015 at 12:38:14 PM UTC-5, Jonathan Wakely wrote:
On 6 March 2015 at 17:21, Nicol Bolas wrote:
> Explain to me, the novice C++ programmer, why this thing which doesn't look
> like a template suddenly became a template. Explain to me why I have to
> implement it in a header, even though it looks exactly like every other
> non-template function declaration/definition.
>
> To the novice C++ programmer, it isn't "all just programming." Whether
> something is a template matters.

Ah, the "won't somebody think of the children" argument.

The answer to why it suddenly became a template is that its parameter
is a concept, not a type. A concept is a family of types. =C2=A0I don't see
why that should be much harder to teach than "a function template is a
family of functions" and "a class template is a family of types".

If a "family of functions" is so fundamentally different from a regular function that it can't be declared/defined in the same way, why does it look exactly like a regular function? If swapping one identifier for another can so radically change how you go about implementing something, shouldn't it be more syntactically obvious that you've made a major change?

Without the template keyword, it doesn't look like a template. And therefore, it is not immediately obvious that it should be treated as such.


People will learn. Learning that
=C2=A0=C2=A0=C2=A0 void f(auto);
implies template is kid's play compared to some things we expect people to figure out.

--

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