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Re: [Cbor] Deterministic CBOR as a possible DISPATCH item

Carsten Bormann <cabo@tzi.org> Sun, 05 March 2023 12:48 UTC

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From: Carsten Bormann <cabo@tzi.org>
In-Reply-To: <7D5B58AE-3B91-4B35-B40B-75836B8CB22F@wolfmcnally.com>
Date: Sun, 05 Mar 2023 13:48:35 +0100
Cc: Anders Rundgren <anders.rundgren.net@gmail.com>, cbor@ietf.org, Christopher Allen <ChristopherA@lifewithalacrity.com>
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To: Wolf McNally <wolf@wolfmcnally.com>
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Subject: Re: [Cbor] Deterministic CBOR as a possible DISPATCH item
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> On 5. Mar 2023, at 12:29, Wolf McNally <wolf@wolfmcnally.com> wrote:
> 
> Anders,
> 
> Actually the main point of serializing floating point values that have lossless integer representations as integers is to remove ambiguity when dealing with numerous possible encodings of the same value, e.g.: 0.0, -0.0, and 0 (integer). This is basically the same rationale as the other minimal encoding reductions; the primary goal not being space savings per se but deterministic encoding.

This, again, is an application layer view.  In IEEE 754, 0.0 and -0.0 are distinct.  If they are the same in your application, deterministic representation requires *the application* to turn one into the other, before a fully generic encoder gets to handle this number.  Practically speaking, delegation of this work to the encoder works, which then can only be used for applications that do not make that distinction.

Grüße, Carsten

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