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

Carsten Bormann <cabo@tzi.org> Wed, 21 May 2014 15:20 UTC

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From: Carsten Bormann <cabo@tzi.org>
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Date: Wed, 21 May 2014 17:19:56 +0200
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To: John Cowan <cowan@mercury.ccil.org>
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Subject: Re: [Json] I-JSON Topic #5: Numbers
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On 21 May 2014, at 04:07, John Cowan <cowan@mercury.ccil.org> wrote:

> 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.

(Or, more specifically, expect an implementation to internalize this representation as the identical value that would be implied by interpreting 1.1 as an ISO 6093 NR2 floating point number.
Actually, most implementations I’m aware of will internalize 1.1 as something like 2476979795053773/2251799813685248 and not the exact 2476979795053772.8/2251799813685248 = 11/10.)

> Furthermore, an I-JSON sender MUST NOT expect a
> receiver to treat an integer whose absolute value is greater than
> 9007199254740992 as an exact value.

I’m with you on that one.

Grüße, Carsten