220 41140 <20181130020338.GA2787@noemi.bahnhof.se> article Path: news.gmane.org!.POSTED!not-for-mail From: Magnus Fromreide Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Function Parameter of Struct Type -> Named Parameters Date: Fri, 30 Nov 2018 03:03:38 +0100 Lines: 90 Approved: news@gmane.org Message-ID: <20181130020338.GA2787@noemi.bahnhof.se> References: <20181129060523.GA21632@noemi.bahnhof.se> 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 1543543297 22216 195.159.176.226 (30 Nov 2018 02:01:37 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Fri, 30 Nov 2018 02:01:37 +0000 (UTC) User-Agent: Mutt/1.10.1 (2018-07-13) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDELLREETMBRB7VUQLQAKGQEED2KA7A@isocpp.org Fri Nov 30 03:01:33 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-yb1-f200.google.com ([209.85.219.200]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1gSY7Y-0005eu-VA for gclcip-std-proposals@m.gmane.org; Fri, 30 Nov 2018 03:01:33 +0100 Original-Received: by mail-yb1-f200.google.com with SMTP id n195-v6sf2660450yba.5 for ; Thu, 29 Nov 2018 18:03:43 -0800 (PST) ARC-Seal: i=2; a=rsa-sha256; t=1543543423; cv=pass; d=google.com; s=arc-20160816; b=rfi6zAAkc8dogubvA5AnUr8I5i5Ef8u+mVS53LbnpyEz0oIfWCuNKWbVC44J8XrRkI jc8Ono1h6d679JWu9Ak5lnri6Ow96LIR4hWCCcsA8d9kxg6v3kLP4gDPDgu8I2tdRemQ mB1cc+BXhtleqGzOQSEBt5oODpd2fd/rZ/qAoZkZhH8nmmnzp2DkyLUeAyt12dTs1SK6 ltdEYq8X1r1AADE/8wncdUFF2C3wG1Jw63UnpGFW/2tikw4FdZmqW9eMG2QNYGWlLwbe 2b/7WCR6wEoNUTeTNt8L7Ni1wG+Nz1V1mS0tjxpw4WkMZmXkMJV6b6owCSwculU0GFn2 qFFw== ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-unsubscribe:list-subscribe:list-archive:list-help:list-post :list-id:mailing-list:precedence:reply-to:user-agent:in-reply-to :content-disposition:mime-version:references:mail-followup-to :message-id:subject:to:from:date:dkim-signature; bh=AJxPnqZtJ45pvAKug/IztcVhO6EwMd4SiX6PLjSf0H0=; b=qUPJQznVKMH94nvrVcJaMOB72eLN8782d/cfPG5PQFi757F0jgMctcZYR5Kmbax924 ChihzGzHDHQmp7+8ntC5I13JFkCAkDLeWxGYlV+4cPK7snboi34g/gJ5bw///s+JCTyL TeLRkJBQQ69OCYr5hWxQhSXyj/UDHT4TIXs9EUrX3GA8b2hhe5tGtPbAtrFb6GREWmV5 B2G71dHh5PfWvQr6Rr3hYJprqg+OceVPYUyNPpDduN+A9Ofe7QZjzOGvtb5PPn5SNPJQ FmIc9T0or4Mq5xskOmHTWm3UixSRmDZg2Ao0Y1Qie68zvkvANeDxo3JG4Nh0x49IJf4g hifA== ARC-Authentication-Results: i=2; mx.google.com; spf=pass (google.com: domain of magfr@lysator.liu.se designates 130.236.254.3 as permitted sender) smtp.mailfrom=magfr@lysator.liu.se; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=liu.se DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:subject:message-id:mail-followup-to:references :mime-version:content-disposition:in-reply-to:user-agent :x-original-sender:x-original-authentication-results:reply-to :precedence:mailing-list:list-id:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=AJxPnqZtJ45pvAKug/IztcVhO6EwMd4SiX6PLjSf0H0=; b=kVLby4d9mvgfJ0wNu79Rmatc0f6SPGyoWUSZE6UOJhf3xfMKNZY4UZOd/M94XEDZrz k9WFL3EFSYfxMjXVTjp6y+wyeABkBIX7VwtCB+lbIpYFHZsdQE6Pku7BKsZ0QTjQHdwB YpnFgG99b/fGwXio5rR8QsHcY1JyuK4Z5eMmdMAs2wWXnqA/rpbmPqQxCTl8Pai6375p 9tAObvN2pI7fyX+PNEOdFOSj76gusSaZcqqCTZQ09aezQy8aeG4ykdXGfDjJ/4IUdQxD 90y5TaEHAre/u692/15GZQiQVObBPBjPgLbhrea+gaOtvN6JYKo+8hG2FIgO16kJX4RH YyRg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:subject:message-id:mail-followup-to :references:mime-version:content-disposition:in-reply-to:user-agent :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=AJxPnqZtJ45pvAKug/IztcVhO6EwMd4SiX6PLjSf0H0=; b=aNeEYudU19Cxeq1F5KNRCpwDjP1QNr666RHSowbNpTNQU1E49sDv8x4WExd9SGcWZo pD10qPGzLkT+pguTV0w71mwaVOn0RKlIoGJjnktDdz7SRBg+BIUvAFhaLx00VGIwufqf fQr0fdhPIKciEoFbqqe+arRrOVKDQizgEWo7T+nrtCvdb6IcmmPr38tAMJU+LZeXmECs 3FbYziLkrDVghmLQWkbFXOghSHyLAnZnLTHcH2Z4Eol6noKom9txyM6PS2X9smLrYSby zSw9GtqhY5iUZCqTxfmGsZOIRroZM96Rw8BM6Zq7aKekWxuYCyzdON2uBfg X-Gm-Message-State: AA+aEWbVm48sM48b8zzVuk7QMq+KcD/WS803qr79FUozC/UvpGxnJri9 yLlnJN7+iBAK0a6LVJkNTc8HhQ== X-Google-Smtp-Source: AFSGD/XTekwjlZfLKKOZ2xMPdVnp5aIBW88IMMRkPqDTE9KLgfbUOGZhRTkrUm8gazQ9V5mvZcRliQ== X-Received: by 2002:a5b:441:: with SMTP id s1-v6mr2406767ybp.80.1543543422965; Thu, 29 Nov 2018 18:03:42 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 2002:a25:3888:: with SMTP id f130-v6ls1884663yba.15.gmail; Thu, 29 Nov 2018 18:03:41 -0800 (PST) X-Received: by 2002:a25:a1c9:: with SMTP id a67-v6mr4122881ybi.64.1543543421939; Thu, 29 Nov 2018 18:03:41 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1543543421; cv=none; d=google.com; s=arc-20160816; b=A4KNA0zzPOfP7ihwsq1x6QUTlaXxE0I2kg1nCC0l2whroSY1qal7mp3MD8XlpfAg0M 4O8Rc+bwtJQcHAndhu+7Z4bUU28dAdZ8wmaUZ/H39jQxoqhr6pYc+As9U0uUJD+TssVK hJyLcZ7MjpZEEyxXro622DI2P5earORIOUQAunEBXGp6u40LCSL8kv6t0h+PxmozS47h 5Klhv4OoU993ggII4FIIuF9R8RpFDMVnHF6Xg8HvF7NDz14UNJcbqE6Izp1+C/bMRfoN O5kapdpHifOYqzULQGgDn5tXCUGB3fmAOl2938FQJxpcQCL5J2Vzv77tIyHNh6i+L83B KNHQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=user-agent:in-reply-to:content-disposition:mime-version:references :mail-followup-to:message-id:subject:to:from:date; bh=Fe1Age/WDnAd3aDO9g9I0QWW2nzhEsvVrcShYEz/umI=; b=ZQIrS95ZFW2p1S91jQ4fD16PIPw7Lgk1LjggXRC7VdmbfUQMh6PyDOXYhO4f1RZhBm 3WbQ5o6Kfws6l7nfd5OKQxy1bIA5HkQaQEzaPFJBrUyodGCfn8JklRGlN3LbZD4ONxj6 rm7PryMKE+I9GHFEfBpoMS01bpT5XsHslu5O5LPqJaU1syS1X1h8DTxjDXsvHx+qHUrX nibZJIjrSP7gQAmgWyBUBZ7pRDaye/QR/MQY1VfxqjJ6rr/1lkKPwv84QktFK6oAS/Po cuvSF1bi/2UA5BYLz6lpDFJ0hu6WlycLm6nFZevz046f7BQp0Zih/cacQSSq6gM3noXE a6Tg== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of magfr@lysator.liu.se designates 130.236.254.3 as permitted sender) smtp.mailfrom=magfr@lysator.liu.se; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=liu.se Original-Received: from mail.lysator.liu.se (mail.lysator.liu.se. [130.236.254.3]) by mx.google.com with ESMTPS id k6-v6si2534536ywg.46.2018.11.29.18.03.41 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 29 Nov 2018 18:03:41 -0800 (PST) Received-SPF: pass (google.com: domain of magfr@lysator.liu.se designates 130.236.254.3 as permitted sender) client-ip=130.236.254.3; Original-Received: from mail.lysator.liu.se (localhost [127.0.0.1]) by mail.lysator.liu.se (Postfix) with ESMTP id E54524000B for ; Fri, 30 Nov 2018 03:03:39 +0100 (CET) Original-Received: from noemi.bahnhof.se (h-155-4-131-135.NA.cust.bahnhof.se [155.4.131.135]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.lysator.liu.se (Postfix) with ESMTPSA id AED2240007 for ; Fri, 30 Nov 2018 03:03:39 +0100 (CET) Mail-Followup-To: std-proposals@isocpp.org Content-Disposition: inline In-Reply-To: X-Virus-Scanned: ClamAV using ClamSMTP X-Original-Sender: magfr@lysator.liu.se X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of magfr@lysator.liu.se designates 130.236.254.3 as permitted sender) smtp.mailfrom=magfr@lysator.liu.se; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=liu.se 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:41140 Archived-At: On Thu, Nov 29, 2018 at 04:19:25PM +1000, Andrew Tomazos wrote: > On Thu, Nov 29, 2018 at 4:05 PM Magnus Fromreide > wrote: > > > On Thu, Nov 29, 2018 at 02:57:55PM +1000, Andrew Tomazos wrote: > > > 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. > > > > I think this misses a lot of benefits > > > To which benefits do you refer? > > > > and would propose two other rules: > > > > 1. Allow anonymous structs > > Similar to anonymous unions. > > This is already done by VC++ and as an extension by g++ and clang++. > > > > $ cat > t.cc > void f(struct {}) {} > $ g++ t.cc > error: types may not be defined in parameter types > void f(struct {}) {} > > Does this work in VC++? Whats the gcc extension called? The parts are independent, the first part is about allowing anonymous structs in places where structs are allowed today. > > > 2. Implicitly assume that a call to a function wants to call a function > > named > > thus > > > I don't quite follow sorry. My proposal doesn't make any changes to name > lookup of a function call or overload resolution, what changes to overload > resolution are you proposing? Consider void f(struct { int a = 0; int b; }); void f(struct { int b; int c = 0; }); Which one should each of the following call? f({a: 1, b: 2 }): f({b: 1, c: 2 }); f({b: 1}); > > > and see if some overload could fit the provieded tokens, this would > > allow > > void fun(enum { something, other } x); > > to do the right thing as well. > > And what is the right thing? I'm not sure I see how this is related? Look up types in the argument lsts of the possible functions. I will readily admit that I have failed to convey the idea here. /MF -- 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/20181130020338.GA2787%40noemi.bahnhof.se. .