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

John Cowan <cowan@mercury.ccil.org> Tue, 27 May 2014 19:26 UTC

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Date: Tue, 27 May 2014 15:26:25 -0400
From: John Cowan <cowan@mercury.ccil.org>
To: Carsten Bormann <cabo@tzi.org>
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References: <CFA21B5C.4A721%jhildebr@cisco.com> <255B9BB34FB7D647A506DC292726F6E1154629E87D@WSMSG3153V.srv.dir.telstra.com> <CAHBU6isO7oooeN8rH8emx-xuOrs2yzBUrhyJNYYAyzK2-QfF0w@mail.gmail.com> <CAK3OfOih-YO-ncbSc3dVv_O7uHfjRxCDjUpzHmkFG5Dj7kb-xg@mail.gmail.com> <5384C118.4060402@cisco.com> <14DB352D-3D0C-458A-90BE-38BCA8CC98DD@tzi.org> <CAHBU6isjZjfoga_g9efiK1L=Pf40ZQXg8War+k9JDM13quHPOQ@mail.gmail.com> <DF223160-A135-4B8E-A895-53A4BF63AA1E@tzi.org> <5384D0C2.7030407@cisco.com> <62E6DC51-2D3D-4C55-89D8-19810347A9FB@tzi.org>
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Subject: Re: [Json] I-JSON Topic #5: Numbers
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Carsten Bormann scripsit:

>    Software which implements IEEE 754-2008 binary64 (double precision)
>    numbers [IEEE754] is generally available and widely used.
>    Implementations which generate I-JSON messages MUST NOT assume that
>    receiving implementations can process numeric values with greater
>    magnitude or precision than provided by those numbers.  I-JSON
>    messages SHOULD NOT include numbers which express greater magnitude
>    or precision than an IEEE 754 double precision number provides,
>    for example 1E400 or 3.141592653589793238462643383279.  In
>    particular, an I-JSON sender MUST NOT expect a receiver to treat
>    an integer whose absolute value is greater than 9007199254740992
>    (i.e., that is outside the range [-2**53, 2**53], where ** stands
>    for exponentiation) as an exact value.
> 
> This then leads well into the next paragraph:
> 
>    For applications such as cryptography, where exact interchange
>    of much larger numbers is reasonably required, it is RECOMMENDED to
>    encode them in JSON string values.  This requires that the receiving
>    program understand the intended semantic of the value.

+1

-- 
John Cowan          http://www.ccil.org/~cowan        cowan@ccil.org
So they play that [tune] on their fascist banjos, eh?
        --Great-Souled Sam