220 41117 article Path: news.gmane.org!.POSTED!not-for-mail From: Andrew Tomazos Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Function Parameter of Struct Type -> Named Parameters Date: Thu, 29 Nov 2018 14:57:55 +1000 Lines: 118 Approved: news@gmane.org Message-ID: Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="0000000000005b3a27057bc68741" X-Trace: blaine.gmane.org 1543467364 24060 195.159.176.226 (29 Nov 2018 04:56:04 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Thu, 29 Nov 2018 04:56:04 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBD5KHQXXWYPRBYPD7XPQKGQEQS2Y64Y@isocpp.org Thu Nov 29 05:56:00 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-lj1-f198.google.com ([209.85.208.198]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1gSEMq-00068Q-6f for gclcip-std-proposals@m.gmane.org; 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[209.85.220.41]) by mx.google.com with SMTPS id o26-v6sor353410ljj.36.2018.11.28.20.58.08 for (Google Transport Security); Wed, 28 Nov 2018 20:58:08 -0800 (PST) Received-SPF: pass (google.com: domain of andrewtomazos@gmail.com designates 209.85.220.41 as permitted sender) client-ip=209.85.220.41; X-Received: by 2002:a2e:9f0b:: with SMTP id u11-v6mr21572ljk.99.1543467488195; Wed, 28 Nov 2018 20:58:08 -0800 (PST) X-Original-Sender: andrewtomazos@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=ShDZJnxY; spf=pass (google.com: domain of andrewtomazos@gmail.com designates 209.85.220.41 as permitted sender) smtp.mailfrom=andrewtomazos@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:41117 Archived-At: --0000000000005b3a27057bc68741 Content-Type: text/plain; charset="UTF-8" It seems to me that a function that takes a struct combined with C++20 designated initializers gets us very close to named parameters: struct FooParameters { int bar; float baz; }; float foo(FooParameters params) { return (params.bar + 3) * params.baz; } int main() { foo({bar: 4, baz: 3.2}); } If we added some syntactic sugar that... 1. Removed the need to give the parameter struct type a name 2. Introduced the parameter struct members into the function definition scope. ....we would get pretty close: float foo(struct { int bar; float baz }) { return (bar + 3) * baz; } int main() { foo({bar: 4, baz:3.2}); } I'd need to take a look to see if it is ambiguous, but I think we can drop the struct keyword from the above: float foo({int bar; float baz}) { return (bar + 3) * baz; } int main() { foo({bar: 4, baz:3.2}); } This would be equivalent to: struct __A { int bar; float baz }; float foo(__A __a) { auto&& [bar,baz] = __a; return (bar + 3) * baz; } int main() { foo({bar: 4, baz:3.2}); } From a teachability perspective its pretty easy to explain that "a brace-enclosed function parameter is the body of an anonymous struct, the members of which are introduced into the function definition scope." This also seems easy to implement. Thoughts? Worth pursuing? -- 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/CAB%2B4KHLe6zDPRreF2q0zQptUgrO0-_u8VrAOA7Du%2B_KHxhGUnw%40mail.gmail.com. --0000000000005b3a27057bc68741 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
It seems to me that a function that takes a struct combine= d with C++20 designated initializers gets us very close to named parameters= :

struct FooParameters {
=C2=A0 =C2=A0 int bar= ;
=C2=A0 =C2=A0 float baz;
};
float foo(FooPa= rameters params) {
=C2=A0 =C2=A0return (params.bar=C2=A0+ 3) * pa= rams.baz;
}
int main() {
=C2=A0 =C2=A0foo({ba= r: 4, baz: 3.2});
}

If we added some syn= tactic sugar that...
1. Removed the need to give the parameter st= ruct type a name
2. Introduced the parameter struct members into = the function definition scope.

...we would get pre= tty close:

float foo(struct { int bar; float baz }= ) {
=C2=A0 =C2=A0 return (bar=C2=A0+ 3) * baz;
}
<= div>int main() {
=C2=A0 =C2=A0foo({bar: 4, baz:3.2});
}=

I'd need to take a look to see if it is ambig= uous, but I think we can drop the struct keyword from the above:
=
float foo({int bar; float baz}) {
=C2=A0 =C2= =A0 return (bar=C2=A0+ 3) * baz;
}
int main() {
=C2=A0 =C2=A0foo({bar: 4, baz:3.2});
}

This would be equivalent to:

struct __A { int bar; float baz };
float foo(__= A __a) {
=C2=A0 =C2=A0auto&& [bar,baz] =3D __a;
=C2=A0 =C2=A0 return (bar=C2=A0+ 3) * baz;
}
int main() {
=C2=A0 =C2=A0foo({bar: 4, baz:3.2});
}

From a teachability perspective its pret= ty easy to explain that "a brace-enclosed function parameter is the bo= dy of an anonymous struct, the members of which are introduced into the fun= ction definition scope."

This also seems easy= to implement.

Thoughts?=C2=A0 Worth pursuing?

--
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To view this discussion on the web visit https://groups.google.com/a/isocpp.org/d/msgid/std-proposals/CAB%2B4KHLe6z= DPRreF2q0zQptUgrO0-_u8VrAOA7Du%2B_KHxhGUnw%40mail.gmail.com.
--0000000000005b3a27057bc68741-- .