220 4602 article Path: news.gmane.org!not-for-mail From: Ville Voutilainen Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Changing lambda scope Date: Sun, 26 May 2013 19:01:27 +0300 Lines: 148 Approved: news@gmane.org Message-ID: References: <90375ba5-8005-47da-9e84-eee151d0ba0a@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary=001a11c3c42604d11a04dda125de X-Trace: ger.gmane.org 1369584089 9643 80.91.229.3 (26 May 2013 16:01:29 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Sun, 26 May 2013 16:01:29 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBC5JHI7A7ALRBWHDRCGQKGQE7BGBSNQ@isocpp.org Sun May 26 18:01:29 2013 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-ye0-f199.google.com ([209.85.213.199]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1UgdNx-0001bA-AL for gclcip-std-proposals@m.gmane.org; Sun, 26 May 2013 18:01:29 +0200 Original-Received: by mail-ye0-f199.google.com with SMTP id l13sf3670373yen.10 for ; Sun, 26 May 2013 09:01:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=x-beenthere:mime-version:in-reply-to:references:date:message-id :subject:from:to:x-original-sender:x-original-authentication-results :reply-to:precedence:mailing-list:list-id:x-google-group-id :list-post:list-help:list-archive:list-subscribe:list-unsubscribe :content-type; bh=UJ85VSmQMqM8lreZ8T5sC5SlvR604Z56PpINveFv20Q=; b=rdijivg0Wznlf0hsIH3jbA/Xu19BS/MV1d9AteZeK+fpdb2OU2ynaUPY8NiInqo6gC Qy27y9j6EoQ9MVlZfxDU8uTz9UlwEXyI1J9OgIl8TXQrW99sN7ip/l/jajNTsqnWibxM 5hhzFhC+hLtUTA3Du/iaHP0SNSlLp03CaK8TaDKCQnPLJTIGfK7B7pKpaEx9GtVpPKDc Jv8SMyMHRVqVOYCJH0JjSh81uVTyCHYJXNUXE3SjefdMSZYCDxr7HOrRcd55GDR70rFc HxSc9glP7TuGlVNIKPsdIf8u3Llt7ru8g1H9CpnQFrGEXgf7Cfrm5Zd9QAERB8Fw1wYW MqMw== X-Received: by 10.224.200.202 with SMTP id ex10mr13233493qab.8.1369584088371; Sun, 26 May 2013 09:01:28 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.49.24.174 with SMTP id v14ls2603572qef.26.gmail; Sun, 26 May 2013 09:01:27 -0700 (PDT) X-Received: by 10.229.128.95 with SMTP id j31mr9453962qcs.69.1369584087511; Sun, 26 May 2013 09:01:27 -0700 (PDT) Original-Received: from mail-qe0-f41.google.com (mail-qe0-f41.google.com [209.85.128.41]) by mx.google.com with ESMTPS id w8si21548370qag.28.2013.05.26.09.01.27 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Sun, 26 May 2013 09:01:27 -0700 (PDT) Received-SPF: pass (google.com: domain of ville.voutilainen@gmail.com designates 209.85.128.41 as permitted sender) client-ip=209.85.128.41; Original-Received: by mail-qe0-f41.google.com with SMTP id b4so3399918qen.14 for ; Sun, 26 May 2013 09:01:27 -0700 (PDT) X-Received: by 10.224.73.134 with SMTP id q6mr22856958qaj.63.1369584087379; Sun, 26 May 2013 09:01:27 -0700 (PDT) Original-Received: by 10.224.174.143 with HTTP; Sun, 26 May 2013 09:01:27 -0700 (PDT) In-Reply-To: <90375ba5-8005-47da-9e84-eee151d0ba0a@isocpp.org> X-Original-Sender: ville.voutilainen@gmail.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of ville.voutilainen@gmail.com designates 209.85.128.41 as permitted sender) smtp.mail=ville.voutilainen@gmail.com; dkim=pass header.i=@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:4602 Archived-At: --001a11c3c42604d11a04dda125de Content-Type: text/plain; charset=ISO-8859-1 On 26 May 2013 17:50, DeadMG wrote: > Sure. Consider > > namespace range { > template auto operator|(L l, R r) { > return r(std::move(l)); > } > template auto map(T t) { > return [=](auto range) { > auto var = range(); > if (var) return optional ))>::type>(t(*var)); > return std::none; > }; > } > } > int main() { > something > | range::map([]...) > | range::map([]...) > etc > } > > It's part of a range design I am working on. I have implemented everything > I need but the lambda ADL problem means that I can't use lambdas when I > should be able to, because the range-combine operator| can't be found. > > > > Thanks, that looks very reasonable. I'll ask Core for the status quo rationale as a first step. -- --- 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. Visit this group at http://groups.google.com/a/isocpp.org/group/std-proposals/?hl=en. --001a11c3c42604d11a04dda125de Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable



On 26 May 2013 17:50, DeadMG <wolfeinstein@gmail.com><= /span> wrote:
Sure. Consider

namespace range {
=A0 =A0 template<typename R, type= name L> auto operator|(L l, R r<= /span>) {
=A0 =A0 =A0 =A0 return= r(std::move(l));
=A0 =A0 }
=A0 =A0 <= /span>template= <typename T<= span style=3D"color:#660">> auto map(T t) {
=A0 =A0 =A0 =A0 return= [=3D](= auto range) {
=A0 =A0 =A0 =A0 =A0 =A0 auto var =3D range();
=A0 =A0 =A0 =A0 =A0 =A0 if (v= ar) return optional<typename = std::decay<decltype= (t(*var))>::type>(= t(*var));=
=A0 =A0 =A0 =A0 =A0 =A0 return std::none;
=A0 =A0 =A0 =A0 };
=A0 =A0 }
}
int main() {
=A0 =A0 something
=A0 =A0 =A0 =A0 | range::map([]...)
=A0 = =A0 =A0 =A0 | range::map([]...)
=A0 =A0 =A0 =A0 etc
}

It's part of a range design I am working o= n. I have implemented everything I need but the lambda ADL problem means th= at I can't use lambdas when I should be able to, because the range-comb= ine operator| can't be found.




Thanks, that looks ver= y reasonable. I'll ask Core for the status quo rationale as a first ste= p.

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