220 38881 article Path: news.gmane.org!.POSTED!not-for-mail From: mihailnajdenov@gmail.com Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Concepts: Investigating implicit type-name introduction Date: Thu, 28 Jun 2018 01:54:33 -0700 (PDT) Lines: 201 Approved: news@gmane.org Message-ID: References: <0c0da3b7-02f4-4130-9441-5a1385864d39@isocpp.org> <288df009-04d7-404a-b1ed-07b6bd9a71a3@isocpp.org> <427de55b-9ff8-407f-802c-8902422d4746@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_2415_1274319483.1530176073417" X-Trace: blaine.gmane.org 1530175955 32415 195.159.176.226 (28 Jun 2018 08:52:35 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Thu, 28 Jun 2018 08:52:35 +0000 (UTC) Cc: mihailnajdenov@gmail.com, zy@miator.net To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCUJ3A7GRAPRBSWE2LMQKGQEGVAYHHI@isocpp.org Thu Jun 28 10:52:31 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-yb0-f200.google.com ([209.85.213.200]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1fYSfG-0008EP-Ig for gclcip-std-proposals@m.gmane.org; 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Thu, 28 Jun 2018 01:54:35 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 2002:a25:814e:: with SMTP id j14-v6ls2050043ybm.3.gmail; Thu, 28 Jun 2018 01:54:34 -0700 (PDT) X-Received: by 2002:a5b:60f:: with SMTP id d15-v6mr864065ybq.6.1530176073966; Thu, 28 Jun 2018 01:54:33 -0700 (PDT) In-Reply-To: <427de55b-9ff8-407f-802c-8902422d4746@isocpp.org> X-Original-Sender: MihailNajdenov@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:38881 Archived-At: ------=_Part_2415_1274319483.1530176073417 Content-Type: multipart/alternative; boundary="----=_Part_2416_1715642877.1530176073418" ------=_Part_2416_1715642877.1530176073418 Content-Type: text/plain; charset="UTF-8" On Thursday, June 28, 2018 at 12:07:39 AM UTC+3, hubert.rein...@gmail.com wrote: > > On Wednesday, June 27, 2018 at 5:44:13 AM UTC-4, Zhihao Yuan wrote: >> >> Outside the debate of the you-know-that syntax, I think this >> demand is easy to fulfill. I think we can allow multi-argument >> constrained parameters like this: >> >> template >> Out merge(In, In2, Out); >> > "Functions" whose arity are non-obvious are (in my opinion) an unfortunate > aspect of certain languages. > > K&R C gives us the perfectly usable idea of a list of identifiers that > introduce parameters; it even allows further attributes of the parameters > to be declared afterwards: > int f(a, b, c) > int a, b, c; > { return a + b + c; } > > Lines (statements ending in semicolons) could be used to apply constraints. > > template > { Mergeable ; typename Other; } > Out merge(In, In2, Out); > The idea is to be able to introduce the types entirely in terms of the concepts they represent so there would be less chance of errors. For instance someone might pass Other in the place of Out or swap In and In2 (this might or might not be a problem) and so on. In any case, if we don't care of the repetition template requires Mergeable Out merge(In, In2, Out); is the best option > > That is perhaps not as short, but still shorter than: > template > requires Mergeable > Out merge(In, In2, 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. To view this discussion on the web visit https://groups.google.com/a/isocpp.org/d/msgid/std-proposals/d15af942-2e06-4384-b1a5-0fc8cafcd00f%40isocpp.org. ------=_Part_2416_1715642877.1530176073418 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable


On Thursday, June 28, 2018 at 12:07:39 AM UTC+3, h= ubert.rein...@gmail.com wrote:
=
On Wednesday, June 27, 2018 at 5:44:13 AM UTC-4, Zhihao Yu= an wrote:
Outside the debate of= the you-know-that syntax, I think this
demand is easy to ful= fill.=C2=A0 I think we can allow multi-argument
constrained p= arameters like this:

=C2=A0=C2=A0=C2=A0 templa= te <Mergeable In In2 Out, class Other>
=C2=A0 =C2=A0 Ou= t merge(In, In2, Out);
"Functions" who= se arity are non-obvious are (in my opinion) an unfortunate aspect of certa= in languages.

K&R C gives us the perfectly usable idea of a list= of identifiers that introduce parameters; it even allows further attribute= s of the parameters to be declared afterwards:
int f(a, b, c)
=C2=A0 int a, b, c;
{ return = a + b + c; }

Lines (statements ending in semicolons) could be= used to apply constraints.

template <In, In2, Out, Other>
{ Mergeable <In, In2, = Out>; typename Other; }
Out merge(In, In2, Out);

The idea is to be able to introduce the type= s entirely in terms of the concepts they represent so there would be less c= hance of errors.=C2=A0
For instance someone might pass Other in the place of Out or swap = In and In2 (this might or might not be a problem) and so on.

In any ca= se, if we don't care of the repetition

template <typename In, In2, Out, Other&g= t;
=C2= =A0 requires Mergeable<In, In2, Out>
Out merge(In, In2, Out);=
=
is the = best option



That is perhaps not as short, but still sho= rter than:
template &l= t;typename In, typename In2, typename Out, typename Other>
requires M= ergeable<In, In2, Out>
Out merge(In, In2, Out);
=
=C2=A0

--
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To unsubscribe from this group and stop receiving emails from it, send an e= mail to std-proposa= ls+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/d15af942-2e06-4384-b1a5-0fc8cafcd00f= %40isocpp.org.
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