220 17363 article Path: news.gmane.org!not-for-mail From: Faisal Vali Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: N4461 (Static if resurrected) -- on implementability Date: Thu, 16 Apr 2015 06:32:16 -0500 Lines: 71 Approved: news@gmane.org Message-ID: References: <96b876e7-1ee0-41de-8ca9-842ef38206f3@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Trace: ger.gmane.org 1429183950 22030 80.91.229.3 (16 Apr 2015 11:32:30 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Thu, 16 Apr 2015 11:32:30 +0000 (UTC) To: "" Original-X-From: std-proposals+bncBDDKRIXX5YARBQF3X2UQKGQEBSNU7JQ@isocpp.org Thu Apr 16 13:32:19 2015 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-vn0-f69.google.com ([209.85.216.69]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1Yii1r-00079S-1Z for gclcip-std-proposals@m.gmane.org; Thu, 16 Apr 2015 13:32:19 +0200 Original-Received: by vnbg62 with SMTP id g62sf108326356vnb.3 for ; Thu, 16 Apr 2015 04:32:18 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:reply-to:in-reply-to:references :date:message-id:subject:from:to:content-type :content-transfer-encoding:x-original-sender :x-original-authentication-results:precedence:mailing-list:list-id :list-post:list-help:list-archive:list-subscribe:list-unsubscribe; bh=z24/S8/4lBWR0Zs2GF0CqWNS6nRf3Kf5jypdW9iAZb4=; b=PpnAd0CZwxnFVe6pcdX+tRbdW5VYdiinqn7FDavAZ8Fjz1T6yTVQmkokngyN7a8bZ7 xiRFuQb0MVAEXJ5NndDnOruVygO1w8TixgWkZNnuvsXl1kzh34qdszV+sONrdJkOOU/j lZrmBXKQlmQM6xcCRaGxLkhcRGFzdfVXTzcHaqmlcBvXI+a6fmYeNFX4u8t1sBB/OjtP Qr2/fruC0YWuSSsyhChSUnEbxP80SwG9DMOYfYa0b3gehho6LhkBViTxUkw/JKcxQPie Z0IwuvuPOUUrF9m98/VT2QjgV6vApzC12PlvZXfaw25awDg5GNLMdO/vwUZ7y/1uL+uh 6Iyw== X-Gm-Message-State: ALoCoQnbY0GIPqrXf5NW2aWY0gzpnLT7MQcgBdwVru5Tjw5MyQ1HrDNGzyipewjQB+cl3aJhrQDs X-Received: by 10.52.189.7 with SMTP id ge7mr40873994vdc.6.1429183937978; Thu, 16 Apr 2015 04:32:17 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.107.39.140 with SMTP id n134ls876358ion.51.gmail; Thu, 16 Apr 2015 04:32:16 -0700 (PDT) X-Received: by 10.42.10.132 with SMTP id q4mr35963189icq.62.1429183936780; Thu, 16 Apr 2015 04:32:16 -0700 (PDT) Original-Received: from mail-ig0-x22c.google.com (mail-ig0-x22c.google.com. [2607:f8b0:4001:c05::22c]) by mx.google.com with ESMTPS id jd2si15826887igb.57.2015.04.16.04.32.16 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 16 Apr 2015 04:32:16 -0700 (PDT) Received-SPF: pass (google.com: domain of faisalv@gmail.com designates 2607:f8b0:4001:c05::22c as permitted sender) client-ip=2607:f8b0:4001:c05::22c; Original-Received: by igbyr2 with SMTP id yr2so74680182igb.0 for ; Thu, 16 Apr 2015 04:32:16 -0700 (PDT) X-Received: by 10.107.12.158 with SMTP id 30mr40811639iom.61.1429183936322; Thu, 16 Apr 2015 04:32:16 -0700 (PDT) Original-Received: by 10.50.176.170 with HTTP; Thu, 16 Apr 2015 04:32:16 -0700 (PDT) In-Reply-To: <96b876e7-1ee0-41de-8ca9-842ef38206f3@isocpp.org> X-Original-Sender: faisalv@gmail.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of faisalv@gmail.com designates 2607:f8b0:4001:c05::22c as permitted sender) smtp.mail=faisalv@gmail.com; dkim=pass header.i=@gmail.com; dmarc=pass (p=NONE dis=NONE) header.from=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:17363 Archived-At: On Thu, Apr 16, 2015 at 4:58 AM, Andrzej Krzemie=C5=84ski wrote: > Hi All, > I think that the "implementability" section of the paper on reduced stati= c > if proposal is too pessimistic. I think I would agree with you - but I never know until i start implementing these things (unlike certain clang Gallifreyans - *cough* Richard *cough* - who see all implementation-potentialities at once). I believe the implementation in clang could be fairly straightforward - in very broad buggy strokes consider: - create a new AST Node that inherits from Stmt that stores the condition stmt, and the two AST branches - if the AST node is not being parsed within a template (i.e. not in a dependent context, and the condition's truth value can be determined then), then consider lexing but not parsing the false branch??, else within a dependent context, parse both arms as we would any compound-stmt within a template definition - when instantiating a function template body, evaluate then the static-if's condition, and then decide which branch to instantiate - and then in the instantiated body replace the entire static-if node, with the transformed compound statement... Am I missing something obvious (or not so obvious)? OK back to trying to get that pesky constexpr lambda proposal done in time prior to lenexa - ( FYI - Geneva can be very distracting ... ;) -faisal > I tried to implement the two examples from > "Motivation" section in C++14 with generic lambdas using the technique > indicated by Paul Fultz II here: > http://www.reddit.com/r/cpp/comments/295e77/clever_overloading_andrzejs_c= _blog/ > > You can see the result here: > http://melpon.org/wandbox/permlink/ub4qmpDyIzkZWP1x > > While the syntax is obviously more ugly than what the paper describes, I > believe the result is achievable in C++14 already. The compiler would onl= y > need to mechanically transform one notation into another. > > Regards, > &rzej > > -- > > --- > 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/. --=20 ---=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. Visit this group at http://groups.google.com/a/isocpp.org/group/std-proposa= ls/. .