220 16766 article Path: news.gmane.org!not-for-mail From: "'Geoffrey Romer' via ISO C++ Standard - Discussion" Newsgroups: gmane.comp.lang.c++.isocpp.general,gmane.comp.lang.c++.isocpp.proposals Subject: Re: [c++std-core-27199] Re: [std-proposals] Re: Re: An implementation of enhanced auto deduction and abbreviated template syntax using Clang Date: Thu, 5 Mar 2015 10:10:44 -0800 Lines: 148 Approved: news@gmane.org Message-ID: References: <7c7d06ea-1e25-4720-9486-ec068b514ea6@isocpp.org> Reply-To: std-discussion@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary=001a11c1092e86533805108e7c3e X-Trace: ger.gmane.org 1425579048 11874 80.91.229.3 (5 Mar 2015 18:10:48 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Thu, 5 Mar 2015 18:10:48 +0000 (UTC) Cc: "std-proposals@isocpp.org" , "std-discussion@isocpp.org" , Faisal Vali To: c++std-core@accu.org Original-X-From: std-discussion+bncBD74DCN5SYHBBJNY4KTQKGQEUMRX75A@isocpp.org Thu Mar 05 19:10:47 2015 Return-path: Envelope-to: gclcig-std-discussion@m.gmane.org Original-Received: from mail-oi0-f71.google.com ([209.85.218.71]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1YTaEQ-00067H-MK for gclcig-std-discussion@m.gmane.org; Thu, 05 Mar 2015 19:10:46 +0100 Original-Received: by oiba3 with SMTP id a3sf74719800oib.2 for ; Thu, 05 Mar 2015 10:10:45 -0800 (PST) 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:cc: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=6ggUCxp3OyKMNGJfa4FPC2vwWOkie/GWMNHXxQxaDrc=; b=fF2fssraVIdM7fbdkqLW82SCy3IueKVEA1axhk471qenFfXHXX9gX4OcwPJ2jMsxqI 5Hxsja5CVRmgFbvYjeaEYWvIRKMG2hcP48pyk/AFQitE3xhWKKqLSHtQWzORawZxKXu2 s9IREj0RU7nN1VObZ92yKfXU2UoqveAeMCj8q0LCv1vnvcC2VftOVxF8R4x78NDPBizJ vu2UKxe1ikMPh0FTwsi36CKBc0Jkx6IcwAuoSvqb6vuo28pCNYcn9UirrDhoOqK68l/1 x3uoYqwnrPxPFxHEOUxN/hA15PjM4KIwHNAg7/g/mAHe54wY+oc3VwlOr+16jrrwmqii DSIA== X-Gm-Message-State: ALoCoQm7UhSzIiKKD2iAd/MELlFziZ/z8PKqugoHinIjRXC2OJtr62X7LoYxp8HJ5SreV/7IV0Lv X-Received: by 10.182.163.108 with SMTP id yh12mr11281134obb.43.1425579045486; Thu, 05 Mar 2015 10:10:45 -0800 (PST) X-BeenThere: std-discussion@isocpp.org Original-Received: by 10.140.107.182 with SMTP id h51ls1272086qgf.91.gmail; Thu, 05 Mar 2015 10:10:44 -0800 (PST) X-Received: by 10.55.52.200 with SMTP id b191mr20764375qka.46.1425579044736; Thu, 05 Mar 2015 10:10:44 -0800 (PST) Original-Received: from mail-qg0-x231.google.com (mail-qg0-x231.google.com. [2607:f8b0:400d:c04::231]) by mx.google.com with ESMTPS id i204si6656205qhc.53.2015.03.05.10.10.44 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 05 Mar 2015 10:10:44 -0800 (PST) Received-SPF: pass (google.com: domain of gromer@google.com designates 2607:f8b0:400d:c04::231 as permitted sender) client-ip=2607:f8b0:400d:c04::231; Original-Received: by qgdz107 with SMTP id z107so6611871qgd.4 for ; Thu, 05 Mar 2015 10:10:44 -0800 (PST) X-Received: by 10.140.34.168 with SMTP id l37mr13811958qgl.28.1425579044122; Thu, 05 Mar 2015 10:10:44 -0800 (PST) Original-Received: by 10.96.179.229 with HTTP; Thu, 5 Mar 2015 10:10:43 -0800 (PST) In-Reply-To: X-Original-Sender: gromer@google.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of gromer@google.com designates 2607:f8b0:400d:c04::231 as permitted sender) smtp.mail=gromer@google.com; dkim=pass header.i=@google.com; dmarc=pass (p=REJECT dis=NONE) header.from=google.com Precedence: list Mailing-list: list std-discussion@isocpp.org; contact std-discussion+owners@isocpp.org List-ID: X-Google-Group-Id: 495566654649 List-Post: , List-Help: , List-Archive: List-Subscribe: , List-Unsubscribe: , X-Original-From: Geoffrey Romer Xref: news.gmane.org gmane.comp.lang.c++.isocpp.general:4977 gmane.comp.lang.c++.isocpp.proposals:16766 Archived-At: --001a11c1092e86533805108e7c3e Content-Type: text/plain; charset=UTF-8 On Thu, Mar 5, 2015 at 9:25 AM, Nevin Liber wrote: > On 5 March 2015 at 11:11, 'Geoffrey Romer' via ISO C++ Standard - Future > Proposals wrote: > >> >> This doesn't convey any useful information: >>> >>> template >>> void frob(T); >>> >> >> I don't agree; it tells me that frob is a generic operation that works >> with roughly any type T. >> > > But what does that mean? Sure, I can copy/move it (since it was passed by > value), but any other constraints will be dictated by the body of frob. > My point is that the use of a generic, meaningless parameter name like "T" tacitly documents the fact that frob isn't going to dictate many additional constraints, beyond perhaps highly generic ones like being able to compare for equality. > > >> >> >>> so in terms of describing the interface it's no different when written >>> like this: >>> >>> void frob(auto); >>> >> >> This is different because now I don't know anything about the >> requirements or semantics of the parameter type. >> > > I'm just not seeing how that is any different (other than the incredibly > minor of having to call decltype on its parameter to get its type). > > Do you have an example function body that works with frob(T) but doesn't > work with frob(auto) (or vice versa) for a specific concrete type? I'm > really trying to understand the difference you see between these two forms. > I'm not aware of any code that will work with one form but not the other. My point is simply that "auto" conveys less information to me as a human reader than a named template parameter would. > -- > Nevin ":-)" Liber (847) 691-1404 > -- --- You received this message because you are subscribed to the Google Groups "ISO C++ Standard - Discussion" group. To unsubscribe from this group and stop receiving emails from it, send an email to std-discussion+unsubscribe@isocpp.org. To post to this group, send email to std-discussion@isocpp.org. Visit this group at http://groups.google.com/a/isocpp.org/group/std-discussion/. --001a11c1092e86533805108e7c3e Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable

= On Thu, Mar 5, 2015 at 9:25 AM, Nevin Liber <nevin@eviloverlord.com= > wrote:
<= span class=3D"">On 5 March 2015 at 11:11, 'Geoffrey Romer' via ISO = C++ Standard - Future Proposals <std-proposals@isocpp.org> wrote:

This doesn't convey any useful information:

template<typename T>
=C2=A0 void frob(T);

I don't= agree; it tells me that frob is a generic operation that works with roughl= y any type T.

But what does that mean?=C2=A0 Sure, I can copy/move it (since it was pas= sed by value), but any other constraints will be dictated by the body of fr= ob.

My point is tha= t the use of a generic, meaningless parameter name like "T" tacit= ly documents the fact that frob isn't going to dictate many additional = constraints, beyond perhaps highly generic ones like being able to compare = for equality.
=C2=A0
=C2=A0
=C2=A0
so in terms of describing the interface it'= ;s no different when written
like this:

void frob(auto);

This is differe= nt because now I don't know anything about the requirements or semantic= s of the parameter type.

I'm just not seeing how that is any different (other than = the incredibly minor of having to call decltype on its parameter to get its= type).

Do you have an example function body that = works with frob(T) but doesn't work with frob(auto) (or vice versa) for= a specific concrete type?=C2=A0 I'm really trying to understand the di= fference you see between these two forms.

I'm not aware of any code that will work with on= e form but not the other. My point is simply that "auto" conveys = less information to me as a human reader than a named template parameter wo= uld.
=C2=A0
=
-= -
=C2=A0Nevin ":-)" Liber=C2=A0 <mailto:nevin@eviloverlord.com&g= t;=C2=A0 (847) 691-1404

--

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