220 5966 article Path: news.gmane.org!not-for-mail From: Ville Voutilainen Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Properties Syntax Date: Thu, 29 Aug 2013 08:25:50 +0300 Lines: 153 Approved: news@gmane.org Message-ID: References: <5e23a0e9-2bd9-4f62-aa83-47bea8144eae@isocpp.org> <5458c2e0-2e03-444e-a34d-4960a07b94ad@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary=001a11c2cbf2cd39a804e50f5613 X-Trace: ger.gmane.org 1377753952 637 80.91.229.3 (29 Aug 2013 05:25:52 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Thu, 29 Aug 2013 05:25:52 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBC5JHI7A7ALRBXVW7OIAKGQE5KVDFPA@isocpp.org Thu Aug 29 07:25:53 2013 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-qa0-f70.google.com ([209.85.216.70]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1VEujw-0003UR-5I for gclcip-std-proposals@m.gmane.org; Thu, 29 Aug 2013 07:25:52 +0200 Original-Received: by mail-qa0-f70.google.com with SMTP id ii20sf425449qab.9 for ; Wed, 28 Aug 2013 22:25:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=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=JTBaSJn3ZcR2ZXhTBq58LuA2xQUQzk/mGa+yjNwsImg=; b=fy4i0CpfXdOWeDKiEpEC4tplvEyldg7/70IZorH0uEwsNwOC+9LebQ7hoGV3HikI5E 1qVX9BSS9+BYOeUpr8wmd8gOM0OGCGWP900mYxqM+d60CqneCdgCvBpBr5R3xj6SgvHU 2pAliK4IFmkNAxkiyYnPsnIJjJwQfC7UjCcol5Ahx2URnIgfxDIrpTkpi40403Q/S6WH GvjxEurcNbocBm2CUhMQw8pveT5VB3t3LDYwm9hRyP3ieKHR+RORbGYqhLy16Hsc4IxI FyoNPyeZYi9FpcLwFFuSLoFCUjjv5VVg9tSrPwttKZf1Ax9b40xwQ9tljw9mtSAzVVcb T9+A== X-Received: by 10.224.223.198 with SMTP id il6mr2502866qab.7.1377753951128; Wed, 28 Aug 2013 22:25:51 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.49.96.9 with SMTP id do9ls653136qeb.80.gmail; Wed, 28 Aug 2013 22:25:50 -0700 (PDT) X-Received: by 10.49.130.132 with SMTP id oe4mr325229qeb.86.1377753950616; Wed, 28 Aug 2013 22:25:50 -0700 (PDT) Original-Received: from mail-qc0-x236.google.com (mail-qc0-x236.google.com [2607:f8b0:400d:c01::236]) by mx.google.com with ESMTPS id b3si843048qeg.79.1969.12.31.16.00.00 (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 28 Aug 2013 22:25:50 -0700 (PDT) Received-SPF: pass (google.com: domain of ville.voutilainen@gmail.com designates 2607:f8b0:400d:c01::236 as permitted sender) client-ip=2607:f8b0:400d:c01::236; Original-Received: by mail-qc0-f182.google.com with SMTP id k18so1553695qcv.41 for ; Wed, 28 Aug 2013 22:25:50 -0700 (PDT) X-Received: by 10.224.6.9 with SMTP id 9mr2592352qax.41.1377753950401; Wed, 28 Aug 2013 22:25:50 -0700 (PDT) Original-Received: by 10.224.195.8 with HTTP; Wed, 28 Aug 2013 22:25:50 -0700 (PDT) In-Reply-To: X-Original-Sender: ville.voutilainen@gmail.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of ville.voutilainen@gmail.com designates 2607:f8b0:400d:c01::236 as permitted sender) smtp.mail=ville.voutilainen@gmail.com; dkim=pass header.i=@gmail.com; dmarc=pass (p=NONE dis=NONE) d=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:5966 Archived-At: --001a11c2cbf2cd39a804e50f5613 Content-Type: text/plain; charset=ISO-8859-1 On 29 August 2013 04:42, Nick wrote: > On Wednesday, 28 August 2013 20:59:49 UTC-4, Ville Voutilainen wrote: > > >> >> >> On 29 August 2013 02:04, Nicol Bolas wrote: >> >>> >>> If properties are syntactically a good and wanted thing, then they >>> deserve the dignity of being a proper language feature. And if >>> >>> >> Do people think properties should be a language feature, when they are >> seemingly just one of the many >> things compile-time reflection can provide? >> > > I keep hearing people try to relate reflection to properties. This doesn't > make any sense to me at all. Can you provide a pseudo code example of how a > property would be retrieved using a reflection interface? > > > > Depends on how far people are willing to go with reflection. ;) One of the expectations of people proposing reflection facilities is that 1) you can query the member functions and member data of a type 2) you can customize how a type answers to such queries The part 2 may effectively involve being able to more or less overload operator. or its equivalent so that when queried for a member f() or x, the type can return whatever it pleases, a reference to an existing member of the type itself, a reference to a subobject or a member thereof, or something more dynamic. Completely imaginary, with quite a bunch of potentially controversial facilities: struct X { private: int y; public: template decltype(auto) operator->() { static if (s == "x") { return y; } else { static_assert(false, "no such member"); } } }; The use is then X x; int foo = x.x; or more verbosely, X x; int foo = std::reflection::member(x); -- --- 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/. --001a11c2cbf2cd39a804e50f5613 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable



On 29 August 2013 04:42, Nick <nicolas.jinchereau@gmail= ..com> wrote:
On Wednesday, 28 August 2013 20:59:49 UTC-4, Ville Voutilainen wrote:<= /span>



<= br>
On 29 August 2013 02:04, Nicol Bolas <jmck...@gmail.com> wrote:

If properties are = syntactically a good and wanted thing, then they deserve the dignity of bei= ng a proper language feature. And if


Do people think properties= should be a language feature, when they are seemingly just one of the many=
things compile-time reflection can provide?

I keep hearing people try to relate = reflection to properties. This doesn't make any sense to me at all. Can= you provide a pseudo code example of how a property would be retrieved usi= ng a reflection interface?




Depends on how far peo= ple are willing to go with reflection. ;) One of the expectations of people= proposing
reflection facilities is that
1) you can query = the member functions and member data of a type
2) you can customize how a type answers to such queries

<= /div>
The part 2 may effectively involve being able to more or less ove= rload operator. or its equivalent
so that when queried for a member f() = or x, the type can return whatever it pleases, a reference to an existing m= ember
of the type itself, a reference to a subobject or a member there= of, or something more dynamic.

Completely imaginary, with= quite a bunch of potentially controversial facilities:
struc= t X
{
private:
=A0=A0=A0 int y;
publi= c:
=A0=A0=A0 template<compile_time_string s> decltype(a= uto) operator-><s>()
=A0=A0=A0 {
=A0=A0=A0=A0=A0= =A0=A0 static if (s =3D=3D "x") {
=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 return y;
=A0=A0= =A0=A0=A0=A0=A0 } else {
=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 st= atic_assert(false, "no such member");
=A0=A0=A0=A0= =A0=A0=A0 }
=A0=A0=A0 }
};

The use is then

X x;
int foo =3D x.x;

or more verbosely,
X x;
<= div class=3D"gmail_extra"> int foo =3D std::reflection::member<compiletimestring("x")>= (x);

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