220 34539 article Path: news.gmane.org!.POSTED!not-for-mail From: "Arthur O'Dwyer" Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: base and self built-in keywords Date: Mon, 2 Oct 2017 11:16:05 -0700 Lines: 171 Approved: news@gmane.org Message-ID: References: <9dec3353-3142-43d1-928f-b88ac74951bf@isocpp.org> <63cb64a8-5add-45ff-a856-364d37042b44@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="94eb2c19516c37cb3e055a945ed9" X-Trace: blaine.gmane.org 1506968166 3946 195.159.176.226 (2 Oct 2017 18:16:06 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Mon, 2 Oct 2017 18:16:06 +0000 (UTC) Cc: sergeikrivonos@gmail.com To: "ISO C++ Standard - Future Proposals" Original-X-From: std-proposals+bncBDLZJYWNDQIONBGKZYCRUBDLILPAI@isocpp.org Mon Oct 02 20:16:00 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-wm0-f70.google.com ([74.125.82.70]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1dz5G4-0000PZ-7d for gclcip-std-proposals@m.gmane.org; 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[209.85.220.41]) by mx.google.com with SMTPS id w51sor5703139edd.54.2017.10.02.11.16.06 for (Google Transport Security); Mon, 02 Oct 2017 11:16:06 -0700 (PDT) Received-SPF: pass (google.com: domain of arthur.j.odwyer@gmail.com designates 209.85.220.41 as permitted sender) client-ip=209.85.220.41; X-Received: by 10.80.143.98 with SMTP id 89mr21055634edy.273.1506968165926; Mon, 02 Oct 2017 11:16:05 -0700 (PDT) Original-Received: by 10.80.202.12 with HTTP; Mon, 2 Oct 2017 11:16:05 -0700 (PDT) In-Reply-To: X-Original-Sender: arthur.j.odwyer@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=rUUX4cRn; spf=pass (google.com: domain of arthur.j.odwyer@gmail.com designates 209.85.220.41 as permitted sender) smtp.mailfrom=arthur.j.odwyer@gmail.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=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:34539 Archived-At: --94eb2c19516c37cb3e055a945ed9 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Mon, Oct 2, 2017 at 7:29 AM, Niall Douglas wrote: > >>>> Python supports multiple inheritance too and I'd suggest you clone >>> their super() function rather than invent anything new. >>> >> >> Oh dear. Literally anything would be better than Python's super() >> function. >> Python invents a sort of linearization of the multiple-inheritance tree = (the >> MRO ) so that you can >> manually call super-class __init__ routines (or not) as you choose; i.e.= , >> Python does not have the concept of "constructor" as we understand it in >> C++. It's more like Objective-C's init routines. >> > > A more accurate explanation is that super() would return the native vtabl= e > for the selected inherited class. > Yes, but if we were copying Python, it still wouldn't necessarily be the specific base class that the OP wanted; it would just be the next base class in the Method Resolution Order. It would have to be determined dynamically, depending on the most-derived-type of *this. But I think we're arguing over a hypothetical at this point. Python's really great. Such a deep well of evil power available to the > programmer. > We agree on both of those sentences. :) > This blog post >> points out something I'd never consciously considered before: Python has= no >> non-virtual inheritance (I think?). >> > > More that virtual inheritance is the default for all member functions. Yo= u > need to explicitly ask to call a non-virtualised implementation, which is > via super() actually. > Well yeah all *dispatch* is virtual. But I meant virtual *inheritance*, i.e= .. class Animal(object): pass class Cat(Animal): pass class Dog(Animal): pass class CatDog(Cat, Dog): pass As far as I understand it from like five minutes of research yesterday =E2= =80=94 so, not a lot =E2=80=94 there's no sense in which CatDog has "two" Animal b= ase subobjects.(*) Whereas in C++ it *would* have two Animal base subobjects, unless you added a couple of "virtual" keywords. (* =E2=80=93 I am quite possibly wrong. The CatDog does clearly "remember" = its Animal member behaviors somehow, so it is not completely far-fetched to me that it could "remember" its Animal instance variables. But that's not my *current* mental model of how Python works. Arguably CatDog doesn't even have *any* Animal "base subobjects" and Python doesn't recognize the concept of "subobject"; Animal methods work on CatDog only because duck-typing.) =E2=80=93Arthur --=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 e= mail 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/CADvuK0K81j6BYp4wbkPKfqaRc52vjikCO_Wt-5aDxumLWFg= M6w%40mail.gmail.com. --94eb2c19516c37cb3e055a945ed9 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
On Mon, Oct 2, 2017 at 7:29 AM, Niall Douglas <nia= lldouglas14@gmail.com> wrote:
<= div class=3D"gmail_quote">

Python supports multiple inheritance too an= d I'd suggest you clone their super() function rather than invent anyth= ing new.

Oh dear. Literally any= thing would be better than Python's super() function.
Python = invents a sort of linearization of the multiple-inheritance tree (the MRO) so that you can manually call super-class __ini= t__ routines (or not) as you choose; i.e., Python does not have the concept= of "constructor" as we understand it in C++. It's more like = Objective-C's init routines.

A more accurate explanation is that super() would return the native vtabl= e for the selected inherited class.

Y= es, but if we were copying Python, it still wouldn't necessarily be the= specific base class that the OP wanted; it would just be the next base cla= ss in the Method Resolution Order. It would have to be determined dynamical= ly, depending on the most-derived-type of *this.
But I think we&#= 39;re arguing over a hypothetical at this point.

Python's really great. Such a deep well o= f evil power available to the programmer.

=
We agree on both of those sentences. :)

=C2= =A0




=
(* =E2=80=93 I am quite possibly wrong. The CatDog does clearly "= remember" its Animal member behaviors somehow, so it is not completely= far-fetched to me that it could "remember" its Animal instance v= ariables. But that's not my current mental model of how Python w= orks. Arguably CatDog doesn't even have any Animal "base su= bobjects" and Python doesn't recognize the concept of "subobj= ect"; Animal methods work on CatDog only because duck-typing.)

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