Path: csiph.com!v102.xanadu-bbs.net!xanadu-bbs.net!goblin3!goblin2!goblin.stu.neva.ru!newsfeed.xs4all.nl!newsfeed3.news.xs4all.nl!xs4all!post.news.xs4all.nl!not-for-mail Return-Path: X-Original-To: python-list@python.org Delivered-To: python-list@mail.python.org X-Spam-Status: OK 0.004 X-Spam-Evidence: '*H*': 0.99; '*S*': 0.00; 'float': 0.07; "subject:' ": 0.07; 'suppose': 0.07; 'bits': 0.09; 'correct,': 0.09; 'operator,': 0.09; 'python': 0.11; 'stored': 0.12; "wouldn't": 0.14; 'distinct': 0.16; 'finite': 0.16; 'from:addr:rosuav': 0.16; 'from:name:chris angelico': 0.16; 'nans': 0.16; 'simpson': 0.16; 'sat,': 0.16; 'all.': 0.16; 'wrote:': 0.18; '>>>': 0.22; 'memory': 0.22; '(in': 0.22; 'python?': 0.22; 'recognize': 0.24; '15,': 0.26; 'least': 0.26; 'certain': 0.27; 'header:In-Reply-To:1': 0.27; 'message-id:@mail.gmail.com': 0.30; '(although': 0.31; 'ctypes': 0.31; "d'aprano": 0.31; 'gather': 0.31; 'steven': 0.31; 'figure': 0.32; 'everyone': 0.33; 'not.': 0.33; "i'd": 0.34; 'could': 0.34; 'subject:with': 0.35; 'received:209.85': 0.35; 'received:209.85.220': 0.35; 'but': 0.35; 'received:google.com': 0.35; 'there': 0.35; 'really': 0.36; 'false': 0.36; 'right?': 0.36; 'possible': 0.36; 'received:209': 0.37; 'to:addr:python- list': 0.38; 'fact': 0.38; 'pm,': 0.38; 'to:addr:python.org': 0.39; 'telling': 0.64; 'more': 0.64; 'different': 0.65; 'direct': 0.67; 'detail.': 0.68; 'calculations': 0.84; 'differences': 0.93; '2013': 0.98 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; bh=taITw28f1I5+jafJhUPQrv2P5JTE9lvjq7jTG4mC2cY=; b=rYFeg4B0Qcoi7+9MwBWQ82qCaVTGW9ltuIpyr3EdBWsaNqfeMdmQtgQUMhYgNQ9mii hfGoEsxaiXyRcJRFIgZZ/d/DupLWaOTG/eNwrIk4pJVjsyNXdEWWeHY6lLdDGr4iL09W le1ziJEYTVxEsahFL4eQiS8s7YunwHOCQtOH1fU3LeBxz6tqaJajnPmKpoLBz2jPHwoo Dw6WSYFFzLHcFuHE94RoyK26u2688UfSEJs4R+OhBCRHVJCxb+TYOAfUItKDVDuOrRv/ XNCUOVNHROqbGa30G98rZBkSumDRx7hRI6sYyvkEJj0KnrkfeLBKxH1rZgpfTaTqKuBI VskA== MIME-Version: 1.0 X-Received: by 10.58.214.105 with SMTP id nz9mr1751374vec.58.1371262909263; Fri, 14 Jun 2013 19:21:49 -0700 (PDT) In-Reply-To: <20130615020308.GA71299@cskk.homeip.net> References: <51bbc49f$0$29997$c3e8da3$5496439d@news.astraweb.com> <20130615020308.GA71299@cskk.homeip.net> Date: Sat, 15 Jun 2013 12:21:49 +1000 Subject: Re: Eval of expr with 'or' and 'and' within From: Chris Angelico To: python-list@python.org Content-Type: text/plain; charset=ISO-8859-1 X-BeenThere: python-list@python.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: General discussion list for the Python programming language List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Newsgroups: comp.lang.python Message-ID: Lines: 28 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1371262918 news.xs4all.nl 15883 [2001:888:2000:d::a6]:51229 X-Complaints-To: abuse@xs4all.nl Xref: csiph.com comp.lang.python:48245 On Sat, Jun 15, 2013 at 12:03 PM, Cameron Simpson wrote: > On 15Jun2013 01:34, Steven D'Aprano wrote: > | Everyone is aware that there is more than one NAN, right? > > I was not. Interesting. > > | If my > | calculations are correct, there are 9007199254740992 distinct float NANs > | in Python (although there is no direct way of distinguishing them). > > Wouldn't id() do it? At least in terms of telling them apart? > I gather they're not inspectable in Python? You could recognize one float object as distinct from another, but that's true of all floats: >>> float("1.0") is float("1.0") False All NaNs are different in terms of the == operator, so conceptually there are an infinite number of unique NaNs. The fact that they're stored in memory using a certain number of bits means that there must be a finite number of possible representations, but that's really an implementation detail. I suppose you could figure out the representation differences by fiddling with ctypes (in C I'd just use a union), but that's really all. ChrisA