220 33802 <2fe78db2-1a96-4c22-9439-1c12dea4868e@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: Nicol Bolas Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: properties? Date: Thu, 10 Aug 2017 10:14:31 -0700 (PDT) Lines: 127 Approved: news@gmane.org Message-ID: <2fe78db2-1a96-4c22-9439-1c12dea4868e@isocpp.org> References: <17b1a3ed-1590-21ce-328d-053b86d6fc0b@gmail.com> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_1045_412153231.1502385272060" X-Trace: blaine.gmane.org 1502385279 15114 195.159.176.226 (10 Aug 2017 17:14:39 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Thu, 10 Aug 2017 17:14:39 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCEKFTV6ZUMBB6VIWLGAKGQENFEH5XY@isocpp.org Thu Aug 10 19:14:32 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-pg0-f70.google.com ([74.125.83.70]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1dfr2T-0003PJ-AH for gclcip-std-proposals@m.gmane.org; Thu, 10 Aug 2017 19:14:29 +0200 Original-Received: by mail-pg0-f70.google.com with SMTP id a186sf12941688pge.7 for ; Thu, 10 Aug 2017 10:14:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:message-id:in-reply-to:references:subject:mime-version :x-original-sender:reply-to:precedence:mailing-list:list-id :list-post:list-help:list-archive:list-subscribe:list-unsubscribe; bh=eVdYDlCLCFV5UO8FqRHvUpKdiM0eyckeUtgbOicXH3s=; b=f3/mCvTn93yxjLlAx3mmpRFV8YvL6sDvrBJnjW3Fl/2fEyYq/2tEmmMJNFyvSgvK6k Nw3lTe372ZKmt47Mqdnje1Zwhowibn0zXgOX/78u/v9J1N8treIzfvZI8x9gbQAIfN+U 0DcgiIoD5enQ39YQFZ3DXRKquYCPtGLiPrHkVJJo2mBSGnTJl3BOHs46XYHBzt6W57zu J29MaFD85Huj+CzjpD5xmqp6MculAh1aKcDfPW2Aixt++oAK0mnkAqaAD0WrRbOq9u1Z mHhxZhRcHgYgpqrozA5XVbrbYIYiYPMu7iUCPDUw0Q+8/v3t+Ry2cv+AynSC8j/BND69 Q0vQ== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:message-id:in-reply-to:references:subject:mime-version :x-original-sender:reply-to:precedence:mailing-list:list-id :list-post:list-help:list-archive:list-subscribe:list-unsubscribe; bh=eVdYDlCLCFV5UO8FqRHvUpKdiM0eyckeUtgbOicXH3s=; b=XABHc6YuJjQDXbs/FOdAxTdeciSibsM4qT7gNAx92EFh9y4YQzoho9zxq4k5Qo95YC SDSvk9cpp2bRPPhSHPN5OU2uaFnX98aQvfNYdSU5jMi7cxV/zlmhCnRownERiddlDcid 8Q9B/jxghu9u5WcuPOUAYML85x8Y/5nkq6m+M7t1PIS1YRaSeM/99S+J5ZPSgTw82WQA c7Ax0IEb4cu9g+f6qOO4eST0BEf0WpYbiybYwC084BxY4vh8GCfIBcKkT4XfcAFxURl4 orqlsbDuR+3SDCwLb930zj5F5D6fKpDSPWm7KKM3yat6YHp4KDsCCDHwZUZf1H9Rd9nD qtNA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:message-id:in-reply-to:references :subject:mime-version: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=eVdYDlCLCFV5UO8FqRHvUpKdiM0eyckeUtgbOicXH3s=; b=Vx/nX72rvvABno6C/gI/fBJFfQ41sMRrZMia5lUu0E2hxmdVCjSMiRuju7PFBpietM Ns2IjuFk5VncX/+vP/TPwb3Q+JoFJi3+zWro90Z06Z7gDxJH8o5cRUusrvYFWT+Nez3D lAxa/U2iTB7vJsYGA4g4anBEWZV8c3syWa27iGWGpWj+zCKmTO2CN5L64Bjb1TBTSEv7 QLQYLvkYus3o52ota1DPR8nwuiwy6R22p0X9hCCFuSuaatixaz82YZiEKoABr3KU4TrB gugxZFK+/fx9AEY9jxsPL5v6VYFW4Z4prSPqtqyMv3t1RAKvDcQOPC75CL95BA9kuo3Q UJHg== X-Gm-Message-State: AHYfb5g9/uSr9C3RSonRaDX1G9KHgpcTcCU7mj1UEwTo9AXk5O3QYD8k O2NQmfRSLzaI7qyf X-Received: by 10.98.58.15 with SMTP id h15mr7404676pfa.33.1502385275292; Thu, 10 Aug 2017 10:14:35 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.107.146.87 with SMTP id u84ls7017204iod.11.gmail; Thu, 10 Aug 2017 10:14:32 -0700 (PDT) X-Received: by 10.31.169.17 with SMTP id s17mr65306vke.11.1502385272545; Thu, 10 Aug 2017 10:14:32 -0700 (PDT) In-Reply-To: X-Original-Sender: jmckesson@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:33802 Archived-At: ------=_Part_1045_412153231.1502385272060 Content-Type: multipart/alternative; boundary="----=_Part_1046_1859562261.1502385272060" ------=_Part_1046_1859562261.1502385272060 Content-Type: text/plain; charset="UTF-8" On Thursday, August 10, 2017 at 1:00:01 PM UTC-4, Ville Voutilainen wrote: > > On 10 August 2017 at 19:53, Matthew Woehlke > wrote: > > On 2017-08-10 12:36, Ville Voutilainen wrote: > >> On 10 August 2017 at 19:35, Matthew Woehlke wrote: > >>> I don't think *reflection* can help with CRTP... *metaclasses* on the > >>> other hand... > >> > >> I consider code generation a part of reflection. Introspection is > >> different, and more limited. :P > > > > Ah, I see... language impedance ;-). > > > > (I suspect Nicol and I have the same "understanding" of what > > "reflection" means... i.e. to us, P0707 *builds on* reflection, but > > isn't *part of* reflection.) > > Well, what is part of reflection remains to be seen. We don't have > anything published yet, and > there's been some serious thought to go towards something that's less > template-y than the first reflection > proposals were. In addition to that, we are seriously looking into > what code generating compile-time > facilities should be like (and look like). It seems clear that we want > code transformation and generation > capabilities. Whether metaclasses will be part of that picture is > another matter. > I guess it's more a matter of the fact that it's a *very* far future thing. C++20 is highly unlikely to see purely introspective reflection. So the chance of code generation reflection reaching even C++23 is pretty low. If mixins are a good idea for C++, I just don't see a need for us to hold off until C++23 (at the earliest), just because we think we *might* be able to get them via code generation reflection. If it were right around the corner, that'd be one thing. But when that sort of stuff is still in the design/research project stage, then let's see if we can solve the problem in a more direct way. At least in the meantime. -- 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. To view this discussion on the web visit https://groups.google.com/a/isocpp.org/d/msgid/std-proposals/2fe78db2-1a96-4c22-9439-1c12dea4868e%40isocpp.org. ------=_Part_1046_1859562261.1502385272060 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
On Thursday, August 10, 2017 at 1:00:01 PM UTC-4, Ville Vo= utilainen wrote:
On 10 August 2= 017 at 19:53, Matthew Woehlke <mwoehlk...@gmail.com> wrote:
> On 2017-08-10 12:36, Ville Voutilainen wrote:
>> On 10 August 2017 at 19:35, Matthew Woehlke wrote:
>>> I don't think *reflection* can help with CRTP... *meta= classes* on the
>>> other hand...
>>
>> I consider code generation a part of reflection. Introspection= is
>> different, and more limited. :P
>
> Ah, I see... language impedance ;-).
>
> (I suspect Nicol and I have the same "understanding" of = what
> "reflection" means... i.e. to us, P0707 *builds on* refl= ection, but
> isn't *part of* reflection.)

Well, what is part of reflection remains to be seen. We don't have
anything published yet, and
there's been some serious thought to go towards something that'= s less
template-y than the first reflection
proposals were. In addition to that, we are seriously looking into
what code generating compile-time
facilities should be like (and look like). It seems clear that we want
code transformation and generation
capabilities. Whether metaclasses will be part of that picture is
another matter.

I guess it's more a matter of the fact that i= t's a very far future thing. C++20 is highly unlikely to see pur= ely introspective reflection. So the chance of code generation reflection r= eaching even C++23 is pretty low.

If mixins are a good idea for C++,= I just don't see a need for us to hold off until C++23 (at the earlies= t), just because we think we might be able to get them via code gene= ration reflection. If it were right around the corner, that'd be one th= ing. But when that sort of stuff is still in the design/research project st= age, then let's see if we can solve the problem in a more direct way.
At least in the meantime.

--
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To view this discussion on the web visit https://groups.google.= com/a/isocpp.org/d/msgid/std-proposals/2fe78db2-1a96-4c22-9439-1c12dea4868e= %40isocpp.org.
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