220 40025 <60449422-b543-4949-557a-96435c1c2926@technion.ac.il> article Path: news.gmane.org!.POSTED!not-for-mail From: Eyal Rozenberg Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Named Parameters for C++ Date: Sun, 26 Aug 2018 23:35:10 +0300 Lines: 48 Approved: news@gmane.org Message-ID: <60449422-b543-4949-557a-96435c1c2926@technion.ac.il> References: <5d064165-5a58-4810-90f7-aa3732be92db@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"; format=flowed X-Trace: blaine.gmane.org 1535315599 26199 195.159.176.226 (26 Aug 2018 20:33:19 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Sun, 26 Aug 2018 20:33:19 +0000 (UTC) User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 To: std-proposals@isocpp.org, Nicol Bolas Original-X-From: std-proposals+bncBDHKZN7LR4ARBC46RTOAKGQESDJLZQQ@isocpp.org Sun Aug 26 22:33:15 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-ed1-f70.google.com ([209.85.208.70]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1fu1ik-0006gq-J9 for gclcip-std-proposals@m.gmane.org; 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[192.16.191.27]) by mx.google.com with ESMTPS id g25-v6si1380749edr.396.2018.08.26.13.35.22 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 26 Aug 2018 13:35:23 -0700 (PDT) Received-SPF: pass (google.com: domain of srs0=2jryg=lj=technion.ac.il=eyalroz@cwi.nl designates 192.16.191.27 as permitted sender) client-ip=192.16.191.27; Original-Received: from fester.cwi.nl (fester.cwi.nl [192.16.191.27]) by fester.cwi.nl (8.14.4/8.12.3) with ESMTP id w7QKZN5t016821; Sun, 26 Aug 2018 22:35:23 +0200 Original-Received: from [192.168.0.83] ([87.69.233.180]) (authenticated bits=0) by fester.cwi.nl (8.14.4/8.12.3) with ESMTP id w7QKZH2x016819 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES128-SHA bits=128 verify=NO); Sun, 26 Aug 2018 22:35:21 +0200 In-Reply-To: <5d064165-5a58-4810-90f7-aa3732be92db@isocpp.org> Content-Language: en-US X-Original-Sender: eyalroz@technion.ac.il X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of srs0=2jryg=lj=technion.ac.il=eyalroz@cwi.nl designates 192.16.191.27 as permitted sender) smtp.mailfrom="SRS0=2JRYg=LJ=technion.ac.il=eyalroz@cwi.nl"; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=technion.ac.il 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:40025 Archived-At: Given your described use of designated initializers, how would you feel about something like following proposal: 1. Functions with named parameter support must be marked with a [[named-param]] attribute. 2. Such marked functions get an anonymous struct defined for their parameters, just like FooParams in your example, and what actually gets compiled is void foo(int, int); void foo(_some_autogenerated_foo_params_struct_identifier); 3. Tie thing up syntax-wise so that you can write foo(.x = 5, .y = 12), and also have some sort of syntactic solution for using &foo . Not that I had a dog in this fight, I'm just trying to help map out some possibilities. On 16/08/18 18:42, Nicol Bolas wrote: > This even works through forwarding, but it does require you to > explicitly name the `FoosParams` type at the call site: > > std::function foofunctor = &foo; > foofunctor(FoosParams{.x = 5, .y = 12}); > > Now of course, this way of handling named parameters causes a bunch of > warts. Anytime you want to create such a function, you have to > explicitly create a type for it. Forwarding, or any usage of the > signature, requires using that typename. And while you can forward them, > the forwarding function only sees it as a single struct, not a set of > values. This makes doing things like transforming parameters impossible > (well, without reflection, and even then, your code would have to assume > that the single struct is a set of "parameters" to be transformed). And > so forth. > > But overall, it gets the job done without language changes. It's not > clean, so it won't be used universally or anything, but it works well > enough that it can be used in places where the ambiguity of a call is > worse than having to pass a struct -- 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. 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