Re: [vwrap] ECMA-262 and the Real LLSD type

I did some playing in an ECMAScript implementation of LLSD, following John's
suggestions of serializing NaN, +/- Infinity, and also negative zero, as
strings when serializing to JSON. Round-tripping works like a charm,
assuming of course that you're testing the results using an "asReal"
coercion that follows the same logic, which an LLSD implementation should
be.

Crockford's http://www.json.org/js.html page even hints at this approach at
the bottom, suggesting that non-finite values could be serialized to JSON as
strings.

On Thu, May 6, 2010 at 12:37 PM, Meadhbh Hamrick <ohmeadhbh@gmail.com>wrote;wrote:

> k. so i pinged doug crockford about it. his response was that JSON
> wants to be independent of any floating point standard, and thus only
> represents finite numbers.
>
> so... a) it's not a mistake or an oversight that you can't represent
> NaNs as JSON-Numbers and b) even if it somehow worked in current
> implementations, it's not the intent of the JSON designers, so, it may
> not work in the future.
>
> so do we know how important it is to represent each of the distinct
> non-finite reals?
>
> -cheers
> -meadhbh
> --
> meadhbh hamrick * it's pronounced "maeve"
> @OhMeadhbh * http://meadhbh.org/ * OhMeadhbh@gmail.com
>
>
>
> On Thu, May 6, 2010 at 10:36 AM, Hurliman, John <john.hurliman@intel.com>
> wrote:
> > In draft-hamrick-llsd-00 "3.2. JSON Serialization" it states:
> >
> >   Real  LLSD 'Real' values are represented by the JSON non-terminal
> 'number'.
> >
> > Then later in "Appendix A. ABNF of Real Values" it lists a series of
> strings that can be converted into real values:
> >
> >   negative-infinity =  %x2D.49.6E.66.69,6E.69.74.79   ; "-Infinity"
> >   negative-zero     =  %x2D.5A.65.72.6F               ; "-Zero"
> >   zero              =  %x30.2E.30                     ; "0.0"
> >   positive-zero     =  %x2B.5A.65.72.6F               ; "+Zero"
> >   positive-infinity =  %x2B.49.6E.66.69,6E.69.74.79   ; "+Infinity"
> >   signaling-nan       =  %4E.61.4E.53                   ; "NaNS"
> >   quiet-nan         =  %4E.61.4E.51                   ; "NaNQ"
> >
> > Does this mean that an LLSD real type with a value of -Infinity needs to
> be converted to a JSON string, and would be decoded on the receiving side as
> an LLSD string with value "-Infinity" (that happens to have a valid
> conversion to an LLSD real)? ECMA-262 does not support Infinity, NaN, etc.
> for the JSON 'number' type so it looks like we need to transmit those values
> as strings.
> >
> > John
> > _______________________________________________
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> > vwrap@ietf.org
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> >
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