Re: [Json] I-JSON Topic #5: Numbers

John Cowan <cowan@mercury.ccil.org> Wed, 21 May 2014 18:32 UTC

Return-Path: <cowan@ccil.org>
X-Original-To: json@ietfa.amsl.com
Delivered-To: json@ietfa.amsl.com
Received: from localhost (ietfa.amsl.com [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id EA3B01A06EE for <json@ietfa.amsl.com>; Wed, 21 May 2014 11:32:31 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -3.251
X-Spam-Level:
X-Spam-Status: No, score=-3.251 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, RCVD_IN_DNSWL_LOW=-0.7, RP_MATCHES_RCVD=-0.651] autolearn=ham
Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id mVxf7iwjKBgC for <json@ietfa.amsl.com>; Wed, 21 May 2014 11:32:30 -0700 (PDT)
Received: from earth.ccil.org (earth.ccil.org [192.190.237.11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 43C911A06EB for <json@ietf.org>; Wed, 21 May 2014 11:32:30 -0700 (PDT)
Received: from cowan by earth.ccil.org with local (Exim 4.72) (envelope-from <cowan@ccil.org>) id 1WnBJT-0004r1-KD; Wed, 21 May 2014 14:32:27 -0400
Date: Wed, 21 May 2014 14:32:27 -0400
From: John Cowan <cowan@mercury.ccil.org>
To: Carsten Bormann <cabo@tzi.org>
Message-ID: <20140521183227.GC20653@mercury.ccil.org>
References: <CF841AAE.47D86%jhildebr@cisco.com> <CAHBU6itK5HtSTPWSsHsHUPja90emqU86LsgjrBorkqcUDivS2A@mail.gmail.com> <CF87EB9C.48BB0%jhildebr@cisco.com> <537A5BE0.3020406@cisco.com> <CF9FCEC9.4A4E7%jhildebr@cisco.com> <488AE66E-725D-40B3-9FDA-ADA1018BCF65@tzi.org> <CFA0F09E.4A609%jhildebr@cisco.com> <255B9BB34FB7D647A506DC292726F6E115461FFE59@WSMSG3153V.srv.dir.telstra.com> <20140521020731.GG9283@mercury.ccil.org> <0374DE58-FC77-4CCA-B100-186C1A0701D4@tzi.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <0374DE58-FC77-4CCA-B100-186C1A0701D4@tzi.org>
User-Agent: Mutt/1.5.20 (2009-06-14)
Sender: John Cowan <cowan@ccil.org>
Archived-At: http://mailarchive.ietf.org/arch/msg/json/YXRNpqynxnOFjnx59j38GxIpUI4
Cc: IETF JSON WG <json@ietf.org>
Subject: Re: [Json] I-JSON Topic #5: Numbers
X-BeenThere: json@ietf.org
X-Mailman-Version: 2.1.15
Precedence: list
List-Id: "JavaScript Object Notation \(JSON\) WG mailing list" <json.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/json>, <mailto:json-request@ietf.org?subject=unsubscribe>
List-Archive: <http://www.ietf.org/mail-archive/web/json/>
List-Post: <mailto:json@ietf.org>
List-Help: <mailto:json-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/json>, <mailto:json-request@ietf.org?subject=subscribe>
X-List-Received-Date: Wed, 21 May 2014 18:32:32 -0000

Carsten Bormann scripsit:

> > as an exact value
> 
> What is your definition of this term here?
> 
> The meaning I’m used to for “exact value” implies you shouldn’t
> expect a binary64-based implementation to treat 1.1 as an exact value.

There is a binary64 number which differs from 1.1 by less than an ulp,
and may be identified with it.  This is distinct from the fact
that 1.1 + 1.1 + ... + 1.1 (ten times) is not equal to 11.

-- 
John Cowan          http://www.ccil.org/~cowan        cowan@ccil.org
Newbies always ask:
  "Elements or attributes?
Which will serve me best?"
  Those who know roar like lions;
  Wise hackers smile like tigers.         --a tanka, or extended haiku