220 21055 <074f49c2-454c-4524-a6ec-e471e6c3ac60@isocpp.org> article Path: news.gmane.org!not-for-mail From: Nicol Bolas Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Adding library support for recursive lambdas Date: Wed, 30 Sep 2015 11:35:37 -0700 (PDT) Lines: 75 Approved: news@gmane.org Message-ID: <074f49c2-454c-4524-a6ec-e471e6c3ac60@isocpp.org> References: <0d59ccd2-4156-4c25-90eb-d23990258ec4@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_693_1424448224.1443638138010" X-Trace: ger.gmane.org 1443638144 14219 80.91.229.3 (30 Sep 2015 18:35:44 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 30 Sep 2015 18:35:44 +0000 (UTC) Cc: yegor.derevenets@gmail.com To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCEKFTV6ZUMBB66WWCYAKGQECSRIT7Q@isocpp.org Wed Sep 30 20:35:43 2015 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-oi0-f69.google.com ([209.85.218.69]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1ZhME9-0002Ka-7p for gclcip-std-proposals@m.gmane.org; Wed, 30 Sep 2015 20:35:41 +0200 Original-Received: by oiev17 with SMTP id v17sf69953983oie.1 for ; Wed, 30 Sep 2015 11:35:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=date:from:to:cc:message-id:in-reply-to:references:subject :mime-version:content-type:x-original-sender:reply-to:precedence :mailing-list:list-id:x-spam-checked-in-group:list-post:list-help :list-archive:list-subscribe:list-unsubscribe; bh=al7222zcyWXYpMOxfMn1a5utugIlPBKmc7Bi2e6jjWY=; b=oZFk5k9s6m+Y1DiHe4oqZxv4iQRHVBLkRCBIigBMsuBR5HjhvKLqkJOnvrjs4xtZ2h zQXw8/ZioYxEn6b9OJ635n98AhAo8Md5drHL5ngQ+tBn+ZX5fskyEyCfuVOob3tdFEor rFXB1pVODlIqZY4WguELX4HgH5sI2oohxyFgbxqTel07oWDasAhly8D5sXlfKjWKDmon NTKrsK9r6UPIk99OgfwT+p6Bv5AfKdb4z5INwh5hTHt6nHWMgctTy85dOL2wG64nQfla RHbac02cNNO3fmRmmBbMLUvUF5Gq8poRYiW+WhUJlFdNg3z6gxvItFgAFr2F7J1nIQlV c7VQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:date:from:to:cc:message-id:in-reply-to :references:subject:mime-version:content-type:x-original-sender :reply-to:precedence:mailing-list:list-id:x-spam-checked-in-group :list-post:list-help:list-archive:list-subscribe:list-unsubscribe; bh=al7222zcyWXYpMOxfMn1a5utugIlPBKmc7Bi2e6jjWY=; b=GdjIxGC750dSpHw1gDAZY+tgawKRWsw0pemG+z12qDq07dBtkQ/cGDETPkmxhg2Urr nJQpA04FM5BPIjUYS0xY50rQ2kCYecGurPLUNIEfttYKh3mK+eJ+EI1nS0ZaQgH2MZpC goH1V7Bf2Mn5+tWS+cYCVHoTI4jfgOy0XJz3iqMg7VHfmYNfP38qNwRqGpDqSUmApuER 56IjOaOtXZP3Lq8DPQpVmaBWFwEuLIFK5GXYNS2Y3kExLJQXkS+Q7q1js+dlcVcZ1V28 pK6akojfKWC67jgjmUJe6Gz60gIvOhORmJahdmMUMsjz3x37RyJt7KlsInWMrKh5nJVo Ejdg== X-Gm-Message-State: ALoCoQmNf3hdykK9OML/o5b2Rx/R4ZGmXd1KCrbcEVpoCFcmpCJFcwHO4BH+ZZC7/JyhnSR+AfVW X-Received: by 10.182.24.9 with SMTP id q9mr4688632obf.13.1443638140222; Wed, 30 Sep 2015 11:35:40 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.107.7.210 with SMTP id g79ls385842ioi.40.gmail; Wed, 30 Sep 2015 11:35:38 -0700 (PDT) X-Received: by 10.50.136.163 with SMTP id qb3mr359076igb.12.1443638138907; Wed, 30 Sep 2015 11:35:38 -0700 (PDT) In-Reply-To: <0d59ccd2-4156-4c25-90eb-d23990258ec4@isocpp.org> X-Original-Sender: jmckesson@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:21055 Archived-At: ------=_Part_693_1424448224.1443638138010 Content-Type: multipart/alternative; boundary="----=_Part_694_758126977.1443638138010" ------=_Part_694_758126977.1443638138010 Content-Type: text/plain; charset=UTF-8 In the Design Decisions section, it claims that `y_wrapper` would have the ability to store a value or reference, depending on a template parameter. By default it stores a value, but if you construct one yourself, it can store a reference. That doesn't seem feasible, not in the intended use case. Remember that lambda functions have a name, but they are untypeable. Calling `std::y` (a terrible function name, BTW) uses template argument deduction to figure out what the lambda's type is. But there's no such thing as template argument deduction when instantiating a template class like `y_wrapper`. So... how do you do this: auto fib = y_wrapper([]...); What goes in the ??? part? -- --- 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/. ------=_Part_694_758126977.1443638138010 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
In the Design Decisions section, it claims that `y_wrapper= ` would have the ability to store a value or reference, depending on a temp= late parameter. By default it stores a value, but if you construct one your= self, it can store a reference.

That doesn't seem feasible, not = in the intended use case. Remember that lambda functions have a name, but t= hey are untypeable. Calling `std::y` (a terrible function name, BTW) uses t= emplate argument deduction to figure out what the lambda's type is. But= there's no such thing as template argument deduction when instantiatin= g a template class like `y_wrapper`. So... how do you do this:

= auto fib =3D y_wrapper<???, use_reference>([]...);
<= /div>
What goes in the ??? part?

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