220 32356 <09ec869a-2c1d-4fe8-8295-253e5001edd4@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: Nicol Bolas Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: =?UTF-8?B?UmU6IFtzdGQtcHJvcG9zYWxzXSBSZTogQWRkaW5nIHRoZSBLZXl3b3JkIOKAnGludGVyZg==?= =?UTF-8?B?YWNl4oCdIGluIEMrKw==?= Date: Tue, 9 May 2017 07:39:08 -0700 (PDT) Lines: 184 Approved: news@gmane.org Message-ID: <09ec869a-2c1d-4fe8-8295-253e5001edd4@isocpp.org> References: <9ee212eb-4037-40c4-94c3-57a9a170a4c3@isocpp.org> <1765502.4y06pMOS3s@tjmaciei-mobl1> <45a81e95-d352-49ab-9c6e-7375aa41413c@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_3151_357011682.1494340748237" X-Trace: blaine.gmane.org 1494340749 27774 195.159.176.226 (9 May 2017 14:39:09 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Tue, 9 May 2017 14:39:09 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCEKFTV6ZUMBBDFJY7EAKGQE4DQT2LA@isocpp.org Tue May 09 16:39:05 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-pg0-f72.google.com ([74.125.83.72]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1d86I4-00076n-M2 for gclcip-std-proposals@m.gmane.org; Tue, 09 May 2017 16:39:05 +0200 Original-Received: by mail-pg0-f72.google.com with SMTP id d127sf921696pga.11 for ; Tue, 09 May 2017 07:39:10 -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 :x-spam-checked-in-group:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=+bpGl6TloiaVW/iI1nt7bJuwWe+c/tMXo5SnC2MfOu0=; b=wbfLsKuKrlleJFkjYSyOf7k1TWjsx6qJ7V10kweBj25tYRTR/Dk7TmxH13DmTZSJ1N 1KEZxp8M0GYVC9ElVV5MsM0GVEs/kWLsOx0GH2Ar0fskg5kbD+fA6j+tSfVmsBmVfxjU qhxi3RzjDrqH2urjOl12mY5k6TwuTEgewz6W+a3Atv1ExKd0gGz0lskwdzL3jI8py4GU jgWDawI+gz6QOdzqj13jGyIqKA4Ij/ZgV4V/ardyn+CfF21axL52k+o8z+rqYXVvrT/M Ly6KDLuyWQeDZsxzCUd9OPhZlKFxvX/nss7hRDVNN8IUv4ErjUcChHLwTaF/bh/28LDd Y+Bw== 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 :x-spam-checked-in-group:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=+bpGl6TloiaVW/iI1nt7bJuwWe+c/tMXo5SnC2MfOu0=; b=cXB5AR+Qbfyvs7vazJjR819sD/04MqHbVZLAjHe2/SsqJ7VCF1rDoVj+AUxUb4M15t 5aHNJWgVoj1I6hsu6Pe6OvciwVqPbpXeGydWpBfCP41IRwuC2jxATi/76TkkYOJ3u5df rRXf3ItsJ12G/XHMekFEXcgGo1Ei+sYPaZGYf5nhiMeyyGOWmYdoQ/m7A2d1CW/9DI2S +01DXJR8fL+1x1DRv9iQ+HHX3+SJJMUoDFwMDW3K2+P5RC4uPiqVavfe9DvK34gsRbAp nFoiedWKHd/cba2FqDVZX2jbYpUWNtBPJKynuacUmWe/wPqdDqIeK5otXAo84Io7/hNr 5yqQ== 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=+bpGl6TloiaVW/iI1nt7bJuwWe+c/tMXo5SnC2MfOu0=; b=UMJ8m9tDn9NPOh0WXKuhmk81Yi6aQCKHkoRNbfiWp1J58cOkEfO1nGjVjCbqeb2Bzt C5ss7Y9bdyprfNixnao5/+Gr+jRmCmef4/VOYCHA4HQq87MkxwpAGpWniDZmAvNGJuH8 ijcUXnR4NZ5FMB928cxaOg+DYHboafaBnjQIyo8KkuXCBGtIWUFWNAmS63cgvlJDUqSc 3g54sYvO4MJOA/oCk8bl99Bk5zcSwBFNZgfYiSjoDfN0rSbc+y71nvedF2IDQPKnYZVv +tz2/R+966hsncbY3/0DCgxdMdolJa6IJxxymFJY4DbipoEazwlBq8As/tVA1ghSg42E C4eg== X-Gm-Message-State: AODbwcAK6kJepTmcnuPGvjcZjGjM6WuZ3jw9ZRzRNO9cJJSE+dhFOLkk fU+bqPiJjWWPYg== X-Received: by 10.99.103.198 with SMTP id b189mr104252pgc.156.1494340749611; Tue, 09 May 2017 07:39:09 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.157.5.70 with SMTP id 64ls429043otw.10.gmail; Tue, 09 May 2017 07:39:08 -0700 (PDT) X-Received: by 10.157.40.242 with SMTP id s105mr6083ota.5.1494340748771; Tue, 09 May 2017 07:39:08 -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:32356 Archived-At: ------=_Part_3151_357011682.1494340748237 Content-Type: multipart/alternative; boundary="----=_Part_3152_1491932021.1494340748237" ------=_Part_3152_1491932021.1494340748237 Content-Type: text/plain; charset="UTF-8" On Tuesday, May 9, 2017 at 4:34:19 AM UTC-4, Jakob Riedle wrote: > > *Concerning the Answer by Nicol Bolas* > >> `vector>::value_type` needs to be a specific type (one >> that is the same in all translation units), > > and it's probably best that this type have a well-defined name. And that >> name can't be `Callable`. > > > Yes it can, let me show you why: > > Imagine a pure abstract base class BaseClass and a derived class > *DerivedClass*: > class BaseClass{ > public: > virtual void operator()() = 0; > }; > > class DerivedClass : public BaseClass{ > public: > void operator()() override {/*Whatever*/} > }; > Now imagine a vector of *BaseClass *objects in which e.g. *DerivedClass *objects > can be inserted. > That would have to be a `vector`. Which would be different from `vector`. > Your argument would be, that std::vector::value_type needs to > be a concrete type, *which it is, its BaseClass.* > No, my argument is that `Callable` is a *concept*. Concepts *are not types*; in the current TS, they are either functions or variables, neither of which is a *type*. Therefore, `vector>::value_type` *cannot be* `Callable`. Still that doesn't mean, It will actually be DerivedClass in all > translation units, but thats how this mechanism is supposed to work. > For *Dynamic Concepts, *this is the way, Mingxing Wang proposed it: as > pure virtual base class. > In order to have "dynamic concepts", you need some construct to refer to such a thing, which must by necessity be *different* from how you refer to *static* concepts. `Callable<>` is a static concept, so if you want to make a dynamic concept based on it, you must use some other syntax besides `Callable<>`. That's my point. You can't have `Callable<>` be both a static and dynamic concept. That's why its best to make "dynamic concepts" specifically be types. -- 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/09ec869a-2c1d-4fe8-8295-253e5001edd4%40isocpp.org. ------=_Part_3152_1491932021.1494340748237 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
On Tuesday, May 9, 2017 at 4:34:19 AM UTC-4, Jakob Riedle = wrote:
Concerning the Answer by Nicol Bolas<= /span>
`vect= or<Callable<void()>>::value_type` needs to be a specific type (one that is t= he same in all translation units),=C2=A0
and it&#= 39;s probably best that this type have a well-defined name. And that name c= an't be `Callable<void()>`.

Yes it can, let me show you why:

Imagine a pure abstract base class BaseClass and a derived class <= b>DerivedClass:
class= BaseCl= ass{=C2=A0public:
=C2=A0 virtual void operator()() =3D 0;
};

class DerivedClass : public BaseClass{
=C2=A0public:
=C2=A0 void operator()()<= /span> overrid= e {/*Whatever*/}
}= ;
Now imagine a vector of BaseClass objects in which e.g. DerivedClass objects can be in= serted.

That would have to be a `ve= ctor<BaseClass*>`. Which would be different from `vector<BaseClass= >`.
=C2=A0
Your argument would be, that std::vector<BaseClas= s>::value_type needs to be a concrete type, which it is, its=C2=A0BaseClass.

No, my argument is that `Callable<void()= >` is a concept. Concepts are not types; in the current TS= , they are either functions or variables, neither of which is a type= ..

Therefore, `vector<Callable<void()>>::value_type` c= annot be `Callable<void()>`.

For Dynamic Concepts, this i= s the way, Mingxing Wang proposed it: as pure virtual base class.

In order to have "dynamic concepts"= ;, you need some construct to refer to such a thing, which must by necessit= y be different from how you refer to static concepts. `Callab= le<>` is a static concept, so if you want to make a dynamic concept b= ased on it, you must use some other syntax besides `Callable<>`.
<= br>That's my point. You can't have `Callable<>` be both a sta= tic and dynamic concept. That's why its best to make "dynamic conc= epts" specifically be types.

--
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To view this discussion on the web visit https://groups.google.= com/a/isocpp.org/d/msgid/std-proposals/09ec869a-2c1d-4fe8-8295-253e5001edd4= %40isocpp.org.
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