220 31062 article Path: news.gmane.org!.POSTED!not-for-mail From: Richard Smith Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: new operators (dot, cross, wedge, exponent) Date: Wed, 22 Feb 2017 13:11:44 -0800 Lines: 134 Approved: news@gmane.org Message-ID: References: <53de9adb-1e05-46fc-8ac9-75fb331720fa@isocpp.org> <9bec1bf1-7fa6-faa4-4372-789b91387ce6@gmail.com> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary=001a113c97fecbb3bd054924f2e4 X-Trace: blaine.gmane.org 1487797924 3215 195.159.176.226 (22 Feb 2017 21:12:04 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Wed, 22 Feb 2017 21:12:04 +0000 (UTC) To: "std-proposals@isocpp.org" Original-X-From: std-proposals+bncBDVNBJG4YAIBBJP5W7CQKGQEJ5GOAAQ@isocpp.org Wed Feb 22 22:12:00 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-wr0-f200.google.com ([209.85.128.200]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1cgeCe-0000Q8-22 for gclcip-std-proposals@m.gmane.org; Wed, 22 Feb 2017 22:12:00 +0100 Original-Received: by mail-wr0-f200.google.com with SMTP id q39sf5906687wrb.3 for ; Wed, 22 Feb 2017 13:12:06 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:sender:in-reply-to:references:from :date:message-id:subject:to:x-original-sender :x-original-authentication-results:reply-to:precedence:mailing-list :list-id:x-spam-checked-in-group:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=5Lk62id4t9Dm5vviK70YJosVIMHONG4Nz+KtzeSnZJk=; b=PcSyxSInMQhnSLb+kKWqpnm24HNVbuzLwWLNpcNEdzSh9AGLtHrVmU/jxIJT8vA+Hy ghd+A0oYssjBloAgYWjqCx/ARa8R/zLmqj46rSGfF7DpfjZO2DnwDhjj2FT56TZxMs/X gF6mt2o71wky8jNqWsjvZasxIlLWC5V3OqJ3RfwHZoQg0IxmfsLkAiPsAt0lHB94+UDE qaxIIOS8F0C16AgikdZlZmQB19XeIH5h8KHktl1mX6AdHtRJhQDFoaDsT2hmNqlIqeJP 6DlpwX2si3GijwiBhX+31yyG0QnMdAFLJiiw8HVLp8I/QCQOou/CARyaS2ZmECG+4cyK LPhw== X-Gm-Message-State: AMke39klyTItsWonuZw7Eqx2LB0EQns7IUPtdF1eK0ucZrC/138ZwvPovQmWYCYD1sM6EQ== X-Received: by 10.223.171.81 with SMTP id r17mr1369597wrc.12.1487797926045; Wed, 22 Feb 2017 13:12:06 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.28.10.66 with SMTP id 63ls396747wmk.0.gmail; Wed, 22 Feb 2017 13:12:05 -0800 (PST) X-Received: by 10.223.136.79 with SMTP id e15mr14747952wre.14.1487797925063; Wed, 22 Feb 2017 13:12:05 -0800 (PST) Original-Received: from mail-wr0-x22c.google.com (mail-wr0-x22c.google.com. [2a00:1450:400c:c0c::22c]) by mx.google.com with ESMTPS id w4si4068679wme.115.2017.02.22.13.12.05 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 22 Feb 2017 13:12:05 -0800 (PST) Received-SPF: pass (google.com: domain of metafoo@gmail.com designates 2a00:1450:400c:c0c::22c as permitted sender) client-ip=2a00:1450:400c:c0c::22c; Original-Received: by mail-wr0-x22c.google.com with SMTP id s27so10629473wrb.2 for ; Wed, 22 Feb 2017 13:12:05 -0800 (PST) X-Received: by 10.223.176.70 with SMTP id g6mr25138970wra.12.1487797924631; Wed, 22 Feb 2017 13:12:04 -0800 (PST) Original-Sender: metafoo@gmail.com Original-Received: by 10.80.172.225 with HTTP; Wed, 22 Feb 2017 13:11:44 -0800 (PST) In-Reply-To: <9bec1bf1-7fa6-faa4-4372-789b91387ce6@gmail.com> X-Original-Sender: richard@metafoo.co.uk X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com; spf=pass (google.com: domain of metafoo@gmail.com designates 2a00:1450:400c:c0c::22c as permitted sender) smtp.mailfrom=metafoo@gmail.com Precedence: list Mailing-list: list std-proposals@isocpp.org; contact std-proposals+owners@isocpp.org List-ID: 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:31062 Archived-At: --001a113c97fecbb3bd054924f2e4 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On 22 February 2017 at 11:54, Jonathan M=C3=BCller wrote: > Instead of specifically adding those specific operators, I rather like a > more general solution - that has probably been discussed before: infix > calling notation for functions. > > As an extended uniform call syntax allow a binary function call `f(a, b)` > to be written as `a f b`. > I don't know whether this would work like so, but maybe `a `f` b` or > something like that? > > This would allow the `a cross b` and `a dot b` you wanted. I forget who originally came up with this, but something along these lines is already possible: template struct identity { typedef T type; }; template using identity_t =3D typename identity::type; template struct OperatorLhs { B b; A (*fn)(B, C); friend A operator*(OperatorLhs &&lhs, C c) { return lhs.fn(static_cast(lhs.b), static_cast(c)); } }; template OperatorLhs operator*(identity_t b, A (*fn)(B, C)) { return {static_cast(b), fn}; } struct Vec {}; Vec cross(const Vec &, const Vec &); Vec a, b; Vec x =3D a *cross* b; (where the choice of the "surrounding" operator dictates the precedence of the resulting pseudo-operator). This does not support the operator in question being overloaded (or a template), but you can fix that and package this up into the following form: struct Cross : InfixFunction { Vec operator()(const Vec &, const Vec&) const; // ... more operator() overloads if you want ... }; inline constexpr Cross cross; Vec a, b; Vec x =3D cross(a, b); Vec y =3D a *cross* b; --=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/CAOfiQqm1uLt-mm9-P0z0hEwi%3D6%3DjUoe-DTFf6VMyjjS= pCW5OGg%40mail.gmail.com. --001a113c97fecbb3bd054924f2e4 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
On 2= 2 February 2017 at 11:54, Jonathan M=C3=BCller <jonathanmuelle= r.dev@gmail.com> wrote:
Instead of specifically adding those specific operators, I = rather like a more general solution - that has probably been discussed befo= re: infix calling notation for functions.

As an extended uniform call syntax allow a binary function call `f(a, b)` t= o be written as `a f b`.
I don't know whether this would work like so, but maybe `a `f` b` or so= mething like that?

This would allow the `a cross b` and `a dot b` you wanted.

I forget who originally came up with this, but something al= ong these lines is already possible:


template<typename T> struct identity { typedef T type; };
template<typename T> using identity_t =3D typename identity<T>= ::type;

template<typename A, typename B, typena= me C> struct OperatorLhs {
=C2=A0 B b;
=C2=A0 A (*fn= )(B, C);
=C2=A0 friend A operator*(OperatorLhs &&lhs, C c= ) { return lhs.fn(static_cast<B>(lhs.b), static_cast<C>(c)); }<= /div>
};
template<typename A, typename B, typename C>
OperatorLhs<A, B, C> operator*(identity_t<B> b, A (*fn= )(B, C)) {
=C2=A0 return {static_cast<B>(b), fn};
}


struct Vec {};
Vec cro= ss(const Vec &, const Vec &);

Vec a, b;
Vec x =3D a *cross* b;


= (where the choice of the "surrounding" operator dictates the prec= edence of the resulting pseudo-operator). This does not support the operato= r in question being overloaded (or a template), but you can fix that and pa= ckage this up into the following form:


<= div>struct Cross : InfixFunction<Cross, std::multiplies> {
= =C2=A0 Vec operator()(const Vec &, const Vec&) const;
=C2= =A0 // ... more operator() overloads if you want ...
};
inline constexpr Cross cross;

Vec a, b;
Vec x =3D cross(a, b);
Vec y =3D a *cross* b;

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To view this discussion on the web visit https://groups.google.com/a/isocpp.org/d/msgid/std-proposals/CAOfiQqm1uLt-= mm9-P0z0hEwi%3D6%3DjUoe-DTFf6VMyjjSpCW5OGg%40mail.gmail.com.
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