220 39876 article Path: news.gmane.org!.POSTED!not-for-mail From: Ville Voutilainen Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Named Parameters for C++ Date: Fri, 17 Aug 2018 20:49:16 +0300 Lines: 67 Approved: news@gmane.org Message-ID: References: <823c098a-0fb0-18c3-82f3-e8a8616312f1@gmail.com> 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 1534528035 5736 195.159.176.226 (17 Aug 2018 17:47:15 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Fri, 17 Aug 2018 17:47:15 +0000 (UTC) To: "ISO C++ Standard - Future Proposals" Original-X-From: std-proposals+bncBC5JHI7A7ALRBHMV3TNQKGQEYZXEPFY@isocpp.org Fri Aug 17 19:47:10 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-oi0-f70.google.com ([209.85.218.70]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1fqiq4-0001Oo-HG for gclcip-std-proposals@m.gmane.org; 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[209.85.220.65]) by mx.google.com with SMTPS id 9-v6sor1583316oid.23.2018.08.17.10.49.17 for (Google Transport Security); Fri, 17 Aug 2018 10:49:17 -0700 (PDT) Received-SPF: pass (google.com: domain of ville.voutilainen@gmail.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; X-Received: by 2002:aca:6087:: with SMTP id u129-v6mr3203011oib.99.1534528157323; Fri, 17 Aug 2018 10:49:17 -0700 (PDT) Original-Received: by 2002:a9d:176:0:0:0:0:0 with HTTP; Fri, 17 Aug 2018 10:49:16 -0700 (PDT) In-Reply-To: X-Original-Sender: ville.voutilainen@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=p0VMX9pX; spf=pass (google.com: domain of ville.voutilainen@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=ville.voutilainen@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=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:39876 Archived-At: On 17 August 2018 at 20:37, Nicol Bolas wrote: >> > So if you can't even rely on the standard library's parameter names, you >> > would be unable to write cross-platform code that uses those names. And >> > if >> > you can't even rely on the standard library... what can you rely on? >> >> This problem ceases to be a problem once modules land. > > > And of course, `#include`s of C++ standard library headers are not required > to actually "include" text files (which is why they don't end in `.h`). They > can just be `import` directives under the hood. Or they can include text > files that themselves just import a module. > > That bears thinking about. But at the same time, if we go this route, we > effectively enforce standard libraries to use those names for its > parameters. Names become a de-facto part of their interfaces. That will make > it difficult for standard library implementations to compile on both C++17 > and C++20/whatever-has-modules. It's worth noting that some languages like Common Lisp do standardize the names of some parameters of the standard library functions. So it's not unfathomable; prior to modules, the problem was that we _couldn't_ standardize the names, it was just not possible. What I have established, having had discussions about named arguments on multiple occasions, is that the following pain points are important: 1) it needs to be an opt-in for the author of a library, so no automagic naming. Some library authors do not want users relying on names that the library author didn't expect them to rely on, in order to avoid breakage that wasn't considered beforehand. 2) The standard library part is the other major one; it's a bit embarrassing if the facility can't work with any standard library functions, and prior to modules, it indeed can't. There have been various suggestions to make names part of the ABI and part of the function type, so that the function can't be called without named arguments, in the traditional ordered-unnamed arguments. That makes wrapping such functions in binds and lambdas and whatnot horrible. Lisp, for example, still allows ordered-unnamed calls even if some parameters are declared &key. Making it part of the ABI is likewise nice for some things (changing the names breaks ABI, silent change of meaning doesn't happen for users), but it's unfortunate from other perspectives, like having to invent new manglings and again running into problems with ordered-unnamed calls. I do expect further discussion and proposals for named arguments. Some committee members are trying fairly hard to get named arguments in. -- 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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