220 21439 article Path: news.gmane.org!not-for-mail From: John Yates Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: alias_ptr, restrict_ptr, unaligned_ptr Date: Thu, 8 Oct 2015 11:30:13 -0400 Lines: 60 Approved: news@gmane.org Message-ID: References: <1580933.kjMTu375fQ@tjmaciei-mobl4> <2377636.q9WPHpPlTT@tjmaciei-mobl4> <73acad8c-5bb0-4c97-ada1-833b55af0be6@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary=001a11332d300da4e00521998ad1 X-Trace: ger.gmane.org 1444318216 27758 80.91.229.3 (8 Oct 2015 15:30:16 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Thu, 8 Oct 2015 15:30:16 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDW2ZOHC5EGRBBUY3KYAKGQEV4WTMVA@isocpp.org Thu Oct 08 17:30:16 2015 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-ig0-f198.google.com ([209.85.213.198]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1ZkD95-0006Lp-Ii for gclcip-std-proposals@m.gmane.org; Thu, 08 Oct 2015 17:30:15 +0200 Original-Received: by igcxw12 with SMTP id xw12sf42957234igc.0 for ; Thu, 08 Oct 2015 08:30:14 -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:sender:in-reply-to:references:date :message-id:subject:from:to:content-type: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=KnmNVbH9JQypE2oEWz90ot99ivUO9E/YHn4aF0gJ4Ms=; b=Y+KvnQPnJWGL/sHA1f45x7EP+ZWRkiC9WpRuVLSA9D24gdvPBlqlg+Tedxn4vg+Le2 0/WxtYFtBnakWtGDJ10bhLEPc+y4UDvbSlOTaq8j5MC4AtMaumhEhViEFIi6Fv7baevK /rrFj2r85fxKNd2qtOI7Z6jNrWY15O4o0PcqmL79HzMWKthT0NWl43S/KlxBP8PkvUpf q/3bHaImeQunnycbLDB1m3rp5NEewIN6QTNwo6JrWrl9QUb0WBmBOoNfRWlOacML6UtO YCl9d3V10j/a0s8xcfFi3Zv0zhD0PWdDjGAuvlRDas3SJVtY/+266ZThZFSUtg0p9BJ1 aZ1A== X-Gm-Message-State: ALoCoQluPzRhy2psrqCzTQfxHyEYJz3mxvWPkIlWdB2bHXWTp4A2CUa84DUkl+gJVOCxL0ApwD7P X-Received: by 10.107.40.133 with SMTP id o127mr6685819ioo.27.1444318214770; Thu, 08 Oct 2015 08:30:14 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.107.132.164 with SMTP id o36ls578156ioi.64.gmail; Thu, 08 Oct 2015 08:30:13 -0700 (PDT) X-Received: by 10.66.248.10 with SMTP id yi10mr9019576pac.6.1444318213777; Thu, 08 Oct 2015 08:30:13 -0700 (PDT) Original-Received: from mail-pa0-x22f.google.com (mail-pa0-x22f.google.com. [2607:f8b0:400e:c03::22f]) by mx.google.com with ESMTPS id id4si67253286pbb.33.2015.10.08.08.30.13 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 08 Oct 2015 08:30:13 -0700 (PDT) Received-SPF: pass (google.com: domain of john.yates.sheets@gmail.com designates 2607:f8b0:400e:c03::22f as permitted sender) client-ip=2607:f8b0:400e:c03::22f; Original-Received: by pacgl6 with SMTP id gl6so1498961pac.2 for ; Thu, 08 Oct 2015 08:30:13 -0700 (PDT) X-Received: by 10.67.30.74 with SMTP id kc10mr8529193pad.147.1444318213413; Thu, 08 Oct 2015 08:30:13 -0700 (PDT) Original-Sender: john.yates.sheets@gmail.com Original-Received: by 10.66.159.101 with HTTP; Thu, 8 Oct 2015 08:30:13 -0700 (PDT) In-Reply-To: <73acad8c-5bb0-4c97-ada1-833b55af0be6@isocpp.org> X-Original-Sender: john.yates.sheets@gmail.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of john.yates.sheets@gmail.com designates 2607:f8b0:400e:c03::22f as permitted sender) smtp.mailfrom=john.yates.sheets@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-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:21439 Archived-At: --001a11332d300da4e00521998ad1 Content-Type: text/plain; charset=UTF-8 > > However, IEEE-754 would still be a bit... dubious. > It is one thing to assert that a modern machine uses IEEE-754 data formats. It is quite another to claim that a language processor supports all of the baroque details in the standard, especially those involving NaNs. In particular if huing to IEEE-754 an optimizer's global value numbering can never treat X == X as true if X could possibly be a NaN. This is because IEEE-754 says that even when the two NaN bit patterns are identical NaN == NaN universally returns false. /john -- --- 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/. --001a11332d300da4e00521998ad1 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
However, IEEE-754 would still be a bit... dubious.
<= /blockquote>

It is one thing to assert that a modern mac= hine uses IEEE-754 data formats.=C2=A0 It is quite another to claim that a = language processor supports all of the baroque details in the standard, esp= ecially those involving NaNs.=C2=A0 In particular=C2=A0if huing to IEEE-754= an optimizer's global value numbering can never treat X =3D=3D X as tr= ue if X could possibly be a NaN.=C2=A0 This is because IEEE-754 says that e= ven when the two NaN bit patterns are identical NaN =3D=3D NaN universally = returns false.

/john

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