220 19934 article Path: news.gmane.org!not-for-mail From: David Krauss Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: `std::bitset::contains(const std::bitset&)` Date: Thu, 20 Aug 2015 07:48:58 +0800 Lines: 80 Approved: news@gmane.org Message-ID: References: Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 (Mac OS X Mail 8.2 \(2098\)) Content-Type: multipart/alternative; boundary="Apple-Mail=_029CDFBB-BED5-4B2E-AE75-885028852EF4" X-Trace: ger.gmane.org 1440028175 1819 80.91.229.3 (19 Aug 2015 23:49:35 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 19 Aug 2015 23:49:35 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBAABB4VL2SXAKGQE4Z4A56Q@isocpp.org Thu Aug 20 01:49:26 2015 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-pd0-f200.google.com ([209.85.192.200]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1ZSD6X-0004ZH-Cn for gclcip-std-proposals@m.gmane.org; Thu, 20 Aug 2015 01:49:13 +0200 Original-Received: by pdbnh15 with SMTP id nh15sf36056771pdb.1 for ; Wed, 19 Aug 2015 16:49:07 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:from:content-type:message-id:mime-version :subject:date:references:to:in-reply-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=G6c+QmyGSejF1M9VuSSBrI9sXZ31Rbvyu3eWAzsr+mU=; b=L6akZCRm+PZByo+ieri5fxoykrFJaLNA2VgF1dt/1T82jW9RhK1cacGz6KEGJ6b8VK boemOQqqiaQ2hibg6GChBA0VOpGyp09gOxOA+pnFPA0kMvUrXQ1q0m8qtCxXnNiVYgLs oMUrahrDKa/KnPoHfQk09JnYErLStHgzU9UAnXVD3tbLof1dGgIcBay6DRwCRJcx8Oql llIXM9fuOJM9H9OFkekz5ecLVysFlO+GsVJ4K18DiGsqsnr5Hfsu5cTVSphfEY57MLOP vaXEd+kI0+nSDh24eHDqSVYRLpEeoLPKTeHiZUDUC+jsfyYwBGwOnMyTWcGZZeFFuWjZ CqIg== X-Gm-Message-State: ALoCoQlRusg9/Kf67LzAZXC0wo4jyiV7q/YnhAsCc5VRXj7tK4hPQZ74sOVu64tLzeFIF54CVi2l X-Received: by 10.66.240.138 with SMTP id wa10mr86544pac.43.1440028147186; Wed, 19 Aug 2015 16:49:07 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.50.90.179 with SMTP id bx19ls39276igb.1.gmail; Wed, 19 Aug 2015 16:49:06 -0700 (PDT) X-Received: by 10.70.140.238 with SMTP id rj14mr384230pdb.38.1440028146060; Wed, 19 Aug 2015 16:49:06 -0700 (PDT) Original-Received: from pv33p04im-asmtp001.me.com (pv33p04im-asmtp001.me.com. [17.143.181.10]) by mx.google.com with ESMTPS id ni8si4170693pbc.47.2015.08.19.16.49.06 for (version=TLS1_2 cipher=AES128-GCM-SHA256 bits=128/128); Wed, 19 Aug 2015 16:49:06 -0700 (PDT) Received-SPF: pass (google.com: domain of potswa@mac.com designates 17.143.181.10 as permitted sender) client-ip=17.143.181.10; Original-Received: from [172.20.10.2] (unknown [121.54.44.88]) by pv33p04im-asmtp001.me.com (Oracle Communications Messaging Server 7.0.5.35.0 64bit (built Mar 31 2015)) with ESMTPSA id <0NTC00CCQSTMA710@pv33p04im-asmtp001.me.com> for std-proposals@isocpp.org; Wed, 19 Aug 2015 23:49:04 +0000 (GMT) X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2015-08-20_01:,, signatures=0 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 suspectscore=1 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1412110000 definitions=main-1508190361 In-reply-to: X-Mailer: Apple Mail (2.2098) X-Original-Sender: potswa@mac.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of potswa@mac.com designates 17.143.181.10 as permitted sender) smtp.mailfrom=potswa@mac.com; dmarc=pass (p=NONE dis=NONE) header.from=mac.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:19934 Archived-At: --Apple-Mail=_029CDFBB-BED5-4B2E-AE75-885028852EF4 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 > On 2015=E2=80=9308=E2=80=9320, at 5:10 AM, rhalbersma@gmail.com wrote: >=20 > However, adding those members would only solve this particular problem. I= t would be much more convenient if std::bitset would mimic std::vector and = expose a data() pointer to its unsigned integer blocks. This would allow e.= g. library writers to provide expression templates that facilitate loop fus= ion and eliminate temporaries in multi-term bit-twiddling expressions for b= itsets with more than 64-bits.=20 The expression (a & b).any() already optimized perfectly: http://goo.gl/Gnd= tKj (godbolt.org) Implementations have latitude to use underlying types smaller than unsigned= long, so the return type of data() would be implementation-dependent. Prob= ably its bit ordering, too. --=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. 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On 2015=E2=80=9308= =E2=80=9320, at 5:10 AM, rhalbersma@gmail.com wrote:

However, adding those members would only solve this pa= rticular problem. It would be much more convenient if std::bitset would mim= ic std::vector and expose a data() pointer to its unsigned integer blocks. = This would allow e.g. library writers to provide expression templates that = facilitate loop fusion and eliminate temporaries in multi-term bit-twiddlin= g expressions for bitsets with more than 64-bits. 

The expression (a & b).any() already optimized perfectly:=  http://goo.gl/GndtKj&= nbsp;(godbolt.org)

Implementations have latitu= de to use underlying types smaller than unsigned long, so the return type o= f data() would be implementation-d= ependent. Probably its bit ordering, too.

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