220 39867 article Path: news.gmane.org!.POSTED!not-for-mail From: Jake Arkinstall Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Named Parameters for C++ Date: Fri, 17 Aug 2018 17:17:56 +0100 Lines: 82 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: multipart/alternative; boundary="0000000000009ceb970573a3e7d3" X-Trace: blaine.gmane.org 1534522562 21821 195.159.176.226 (17 Aug 2018 16:16:02 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Fri, 17 Aug 2018 16:16:02 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDCZX3WUUQFRBP7K3PNQKGQECSLAFSI@isocpp.org Fri Aug 17 18:15:58 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-it0-f70.google.com ([209.85.214.70]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1fqhPq-0005Ws-H9 for gclcip-std-proposals@m.gmane.org; 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[209.85.220.41]) by mx.google.com with SMTPS id z19-v6sor896345ioe.331.2018.08.17.09.18.06 for (Google Transport Security); Fri, 17 Aug 2018 09:18:06 -0700 (PDT) Received-SPF: pass (google.com: domain of jake.arkinstall@gmail.com designates 209.85.220.41 as permitted sender) client-ip=209.85.220.41; X-Received: by 2002:a6b:1c8c:: with SMTP id c134-v6mr30562716ioc.305.1534522686236; Fri, 17 Aug 2018 09:18:06 -0700 (PDT) In-Reply-To: <823c098a-0fb0-18c3-82f3-e8a8616312f1@gmail.com> X-Original-Sender: jake.arkinstall@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=WVgXwhk3; spf=pass (google.com: domain of jake.arkinstall@gmail.com designates 209.85.220.41 as permitted sender) smtp.mailfrom=jake.arkinstall@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:39867 Archived-At: --0000000000009ceb970573a3e7d3 Content-Type: text/plain; charset="UTF-8" On Fri, 17 Aug 2018, 16:16 Matthew Woehlke, wrote: > > foo(int :a, int :b = 3, int :c = 12); > foo(1, c: 6); // name *must* be used here because 'b' is omitted > Ah. That does demolish my idea about using strong types as named wrappers for the underlying type. Well, it makes it insufficient, at least - in order to make it work we'd need to change the language to keep trying parameter ordering until the types fit. Unlike an approach that changes mangling directly, this does mean that the following non-named code would become valid: foo(const int& a=1, const std::string& b="hello"); foo("world"); //yuck Which, innocent enough in this example, is going to be a source of bugs when an implicit conversion exists - unless that ordering search matches act as explicit, which is going to cause its own problems in terms of usability. > -- 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/CAC%2B0CCP6nzxYMpKXcCMCvi-6wq0XRGs6PZquBQ9Q4t1q_re3AA%40mail.gmail.com. --0000000000009ceb970573a3e7d3 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable


= On Fri, 17 Aug 2018, 16:16 Matthew Woehlke, <mwoehlke.floss@gmail.= com> wrote:

=C2=A0 foo(int :a, int :b =3D 3, int :c =3D 12);
=C2=A0 foo(1, c: 6); // name *must* be used here because 'b' is omi= tted

Ah. That does demolish my idea about using strong types as named wrappe= rs for the underlying type. Well, it makes it insufficient, at least - in o= rder to make it work we'd need to change the language to keep trying pa= rameter ordering until the types fit.

Unlike an approach that changes mangling directly, this does = mean that the following non-named code would become valid:

foo(const int& a=3D1, const std::str= ing& b=3D"hello");
foo("world&quo= t;); //yuck

Which, innoc= ent enough in this example, is going to be a source of bugs when an implici= t conversion exists - unless that ordering search matches act as explicit, = which is going to cause its own problems in terms of usability.

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