220 33877 <2546050.sL0pCq2xIu@tjmaciei-mobl1> article Path: news.gmane.org!.POSTED!not-for-mail From: Thiago Macieira Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Auto-Pimpl by partial Date: Sun, 13 Aug 2017 13:52:48 -0700 Lines: 58 Approved: news@gmane.org Message-ID: <2546050.sL0pCq2xIu@tjmaciei-mobl1> References: <0e49ee2a-2ead-431d-83ae-54587c1b8c8e@isocpp.org> <1853356.WW4VBYSKBC@tjmaciei-mobl1> <2e940bb4-f8d4-4a02-9802-0036af7efc09@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" X-Trace: blaine.gmane.org 1502657577 16665 195.159.176.226 (13 Aug 2017 20:52:57 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Sun, 13 Aug 2017 20:52:57 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCB4TK757YBRBJPYYLGAKGQE3TVSDNI@isocpp.org Sun Aug 13 22:52:51 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-yw0-f199.google.com ([209.85.161.199]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1dgzsO-0003or-RR for gclcip-std-proposals@m.gmane.org; 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[2a01:4f8:d13:f81:21c:14ff:fe01:12a3]) by mx.google.com with ESMTP id 37si5668779iop.51.2017.08.13.13.52.52 for ; Sun, 13 Aug 2017 13:52:52 -0700 (PDT) Received-SPF: pass (google.com: domain of thiago@macieira.org designates 2a01:4f8:d13:f81:21c:14ff:fe01:12a3 as permitted sender) client-ip=2a01:4f8:d13:f81:21c:14ff:fe01:12a3; Original-Received: from tjmaciei-mobl1.localnet (unknown [IPv6:2601:1c0:4501:5f9f:c73:d163:e3f0:34af]) by gondolin.macieira.info (Postfix) with ESMTPSA id 0D54011B72B for ; Sun, 13 Aug 2017 13:52:49 -0700 (PDT) In-Reply-To: <2e940bb4-f8d4-4a02-9802-0036af7efc09@isocpp.org> X-Original-Sender: thiago@macieira.org X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of thiago@macieira.org designates 2a01:4f8:d13:f81:21c:14ff:fe01:12a3 as permitted sender) smtp.mailfrom=thiago@macieira.org 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:33877 Archived-At: On Sunday, 13 August 2017 01:51:49 PDT Izzy Coding wrote: > I'm not sure exactly how the implementation would work as I have not sat > down to fully flesh it out yet. But, I would hope and strive to ensure zero > overhead where possible. That imples no heap allocation, which means the full object size must be known at any point in the instantiation. That means your feature request is no different than inheritance, with the possible exception of making the partial types non-instantiable without requiring a pure virtual method inside. Of course, you could achieve the same by way of a protected, default constructor (or private if you want to ensure only you can derive from it). The only visible difference I can think of would be the typeid() and reflection of the objects. > Inheritance would require multiple class definitions spread across multiple > sets of .h and .cpp files (or if you like to dump multiple things in a > single file you could do it as 2 files, but I doubt many people do this). Which your proposal also asks for. > Also This allows creation of FirstThing independent of FullThing. No, it doesn't. See above. > Partial just tells the compiler that I don't care what the full size of > Thing is, I just want access to the view I do have a definition for. These > can only be created in full (requiring include of full definition chain so > allocation can happen as normal), but seen and used as a partial view of > that full type as required. A FirstThing is a FullThing, but where I only > care about the size of memory that is defined in first.h. I hope this makes > sense. > > This allows me to spread the definition of a single type across multiple > files so that I can keep my includes as minimal as possible and means the > using class/function only has to know about what it is going to use. I don't see how that is any different from simple inheritance. > Also when used with meta-classes each partial could be defined as a > different meta-class which would include only the required compiler > transforms available to each level of partial. Which would allow the > separation of concerns for each set of functionality in a Thing. Right. -- Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org Software Architect - Intel Open Source Technology Center -- 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/2546050.sL0pCq2xIu%40tjmaciei-mobl1. .