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  • NaN codes?

    From luserdroog@21:1/5 to All on Mon Nov 7 13:21:42 2022
    On a similar tangent to the idea I presented in another thread of re-using the top byte of a 32bit code containing a Unicode code point in the lower bits, there is a space of NaN representations in a double that could be overlaid
    to store or transport data or control metadata in the same channel.

    Under what circumstances would a language implementation wish to
    use NaN codes overlaid in IEEE doubles?

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  • From James Harris@21:1/5 to luserdroog on Tue Nov 8 11:12:26 2022
    On 07/11/2022 21:21, luserdroog wrote:

    On a similar tangent to the idea I presented in another thread of re-using the
    top byte of a 32bit code containing a Unicode code point in the lower bits, there is a space of NaN representations in a double that could be overlaid
    to store or transport data or control metadata in the same channel.

    Under what circumstances would a language implementation wish to
    use NaN codes overlaid in IEEE doubles?

    Hard to say. What you suggest sounds a bit like a solution looking for a problem. It may be better to get everything working with floats and
    metadata occupying separate fields and only combine them later as an optimisation, if you still think it's doable at that time.


    --
    James Harris

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  • From James Cloos@21:1/5 to All on Tue Nov 8 13:10:08 2022
    keep in mind that not all hardware leaves the nan bits alone.

    it seems to be more common of late thast they specify that all nan
    results are canonical nans. whether signalling or quiet.

    that was why R stopped using a specific nan payload to represent its NA
    (Not Available) value. and canonical-only has only gotten more common
    since then.

    -JimC
    --
    James Cloos <[email protected]> OpenPGP: 0x997A9F17ED7DAEA6

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