220 40047 article Path: news.gmane.org!.POSTED!not-for-mail From: Matthew Woehlke Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Named Parameters for C++ Date: Mon, 27 Aug 2018 13:29:46 -0400 Lines: 65 Approved: news@gmane.org Message-ID: References: <5d064165-5a58-4810-90f7-aa3732be92db@isocpp.org> <60449422-b543-4949-557a-96435c1c2926@technion.ac.il> <3e50834d-2e56-392f-fe30-8c24769d7647@gmail.com> <44b180b7-9c2f-48fe-9cf5-5b803b45f460@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" Content-Transfer-Encoding: quoted-printable X-Trace: blaine.gmane.org 1535390864 1432 195.159.176.226 (27 Aug 2018 17:27:44 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Mon, 27 Aug 2018 17:27:44 +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 Original-X-From: std-proposals+bncBC37LBFWUIFBBDHKSDOAKGQEJ2SH3WQ@isocpp.org Mon Aug 27 19:27:40 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-qk0-f198.google.com ([209.85.220.198]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1fuLIg-0000FA-Nx for gclcip-std-proposals@m.gmane.org; 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[66.194.253.20]) by smtp.googlemail.com with ESMTPSA id n24-v6sm10210277qtf.0.2018.08.27.10.29.46 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 27 Aug 2018 10:29:46 -0700 (PDT) Openpgp: preference=signencrypt In-Reply-To: <44b180b7-9c2f-48fe-9cf5-5b803b45f460@isocpp.org> Content-Language: en-US X-Original-Sender: mwoehlke.floss@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=izxjPi1g; spf=pass (google.com: domain of mwoehlke.floss@gmail.com designates 209.85.220.41 as permitted sender) smtp.mailfrom=mwoehlke.floss@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:40047 Archived-At: On 2018-08-27 12:56, mihailnajdenov@gmail.com wrote: > On Monday, August 27, 2018 at 7:22:44 PM UTC+3, Matthew Woehlke wrote: >> On 2018-08-27 12:12, =D0=9C=D0=B8=D1=85=D0=B0=D0=B8=D0=BB =D0=9D=D0=B0= =D0=B9=D0=B4=D0=B5=D0=BD=D0=BE=D0=B2 wrote:=20 >>> How do you envision optional argument would work if we have only=20 >>> named-arguments-part-of-the-type?=20 >> >> ...because named arguments are a special, "magic" type. Basically, when= =20 >> the compiler sees that a function call has a named argument, it alters= =20 >> the overload rules, so that the named argument doesn't have to match the= =20 >> *current* argument, but *any* argument (excluding already matched=20 >> arguments).=20 >=20 > Will the arguments you envision be able to be marked as optional or not? They can be defaulted: void foo(int .x, int .y=3D5, int .z=3D12); foo(2, .z=3D7); // okay, calls foo(2, 5, 7) > Because this "optionality" must travel through the type system as well, t= o=20 > be able to work with async/forward_as_typle > This is not the case of "simple" strong names, which are "simply" mandato= ry=20 > and "are just a different type".=20 I don't think that's the case: void invoke(Func f, tuple> args) { f(get<0>(args), get<1>(args)); } invoke(foo, make_tuple(2, .z=3D7)); // okay, calls foo(2, 5, 7) (Obviously, `invoke` is really a template, but I have shown the instantiation that is called in the example.) This will work with reordering also (if we allow it). I don't need to know anything about optionality when I am forwarding arguments, just so long as when I try to call the actual function, that succeeds with the arguments I actually provided. Basically, by tying the name to each argument, it passes through forwarding transparently, so that when I try to call the "actual" function, the arguments the compiler sees look the same as if the forwarding layer(s) weren't there. ....unless you're talking about something totally different when you talk about "optionality"? --=20 Matthew --=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/fd3cd9e2-26fc-7770-0f82-182abd75134d%40gmail.com= .. .