220 36017 article Path: news.gmane.org!.POSTED!not-for-mail From: Jack Adrian Zappa Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Make aliased templates first class citizens Date: Tue, 19 Dec 2017 05:47:55 -0800 (PST) Lines: 146 Approved: news@gmane.org Message-ID: References: <8e4dd67b-e929-4f83-8f68-4a7ebd20a4e3@isocpp.org> <7eb526d4-c557-443c-a7d5-235dc8e44926@isocpp.org> <6d5434aa-a3bd-460f-bdbd-3db00772768a@isocpp.org> <90bc6ae9-54a4-4fe5-b4ee-a32db51ca820@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_28421_793900392.1513691275161" X-Trace: blaine.gmane.org 1513691159 11989 195.159.176.226 (19 Dec 2017 13:45:59 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Tue, 19 Dec 2017 13:45:59 +0000 (UTC) Cc: adrian.hawryluk@gmail.com To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCULLOGNUQIRBDFR4TIQKGQEFUGENFQ@isocpp.org Tue Dec 19 14:45:55 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-vk0-f71.google.com ([209.85.213.71]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1eRIDT-0002ph-5v for gclcip-std-proposals@m.gmane.org; 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Tue, 19 Dec 2017 05:47:57 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.31.174.76 with SMTP id x73ls5494633vke.21.gmail; Tue, 19 Dec 2017 05:47:56 -0800 (PST) X-Received: by 10.31.178.196 with SMTP id b187mr328233vkf.8.1513691275743; Tue, 19 Dec 2017 05:47:55 -0800 (PST) In-Reply-To: <90bc6ae9-54a4-4fe5-b4ee-a32db51ca820@isocpp.org> X-Original-Sender: adrian.hawryluk@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:36017 Archived-At: ------=_Part_28421_793900392.1513691275161 Content-Type: multipart/alternative; boundary="----=_Part_28422_2016807006.1513691275162" ------=_Part_28422_2016807006.1513691275162 Content-Type: text/plain; charset="UTF-8" On Monday, December 18, 2017 at 3:56:37 PM UTC-5, Marcin Jaczewski wrote: > > > > On Monday, December 18, 2017 at 6:28:12 AM UTC+1, adrian....@gmail.com > wrote: >> >> On Sunday, December 17, 2017 at 8:18:29 PM UTC-5, Marcin Jaczewski wrote: >>> >>> >>> Right now I see only one problem with this: >>> template >>> using B = typename A::template template temp<1><2>; >>> //or >>> template >>> using C = template A::template temp<1>; //this return template not >>> type, this could be problematic when C++20 remove options for different >>> `using` >>> //or >>> template >>> using D = template template A::temp; >>> You will probably need something like this to allow proper handle of `<` >>> and `>` by compiler in dependent context. >>> >> >> I'm not exactly sure what you mean. So, these are potential ways to tell >> the compiler what it should be seeing? temp is a binary operator? What >> is A? Could you please give more context or explain in more detail what >> you are attempting to say? >> > > What is `temp`? This is good question that your proposal should answer > because it's dependent name on template parameter `A`. If we implements > your proposition how you will access it if it is in dependent context? > Right now we have way to distinguish between objects, types and > templates, now with your proposal we will need new way to support your > first class aliases. > Ah, sorry. Not sure how I misread that. If I understand the current parsing of C++, I think your 1st one is most appropriate. Also, could you expand on what you mean by your 2nd item being possibly problematic in c++20? -- 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/a366da24-92ff-4011-99a9-4aca60390142%40isocpp.org. ------=_Part_28422_2016807006.1513691275162 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
On Monday, December 18, 2017 at 3:56:37 PM UTC-5, Marcin J= aczewski wrote:


On Monday, December 18, 2017 at 6:28:12 AM UTC+1, adrian....@g= mail.com wrote:
On Sunday, December 17, 2017 at 8:18:29 PM UTC-5, Marcin Jaczewski wrote:<= blockquote class=3D"gmail_quote" style=3D"margin:0;margin-left:0.8ex;border= -left:1px #ccc solid;padding-left:1ex">

Right now I see= only one problem with this:
template<typename A>
using B =3D typename A::template template temp<1><2>;
//or
template<<= span style=3D"color:#008">typename A>
using C =3D template A::template= temp&l= t;1>= ; //thi= s return template not type, this could be problematic when C++20 remove opt= ions for different `using`
//or
template<typename A>
<= /span>using D = =3D template <= /span>template= A::tem= p;
<= /span>
You will probably need something like this to allo= w proper handle of `<` and `>` by compiler in dependent context.
<= /div>

I'm not exactly sure what you mea= n.=C2=A0=C2=A0So, these are potential ways to tell the compiler what it sho= uld be seeing?=C2=A0 temp is a= binary operator?=C2=A0 What is A?=C2=A0 Could you please give more context or explain in more detail wha= t you are attempting to say?

What is `temp`? Th= is is good question that your proposal should answer because it's depen= dent name on template parameter `A`. If we implements your proposition how = you will access it if it is in dependent context?
Right now we have way = to distinguish between objects, types= and templates, now with your proposal we will need new way to support your= first class aliases.

Ah, sorry.= =C2=A0 Not sure how I misread that.=C2=A0 If I understand the current parsi= ng of C++, I think your 1st one is most appropriate.=C2=A0 Also, could you = expand on what you mean by your 2nd item being possibly problematic in c++2= 0?=C2=A0

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