Re: OK, now I see Re: Motion P1788/M0013.04 - Comparisons - Overflow / Infinity
Ian, P1788, Nate
On 22 Sep 2010, at 06:00, Ian McIntosh wrote:
> I don't think we made a firm decision on how and where decorations are stored, but the general assumption seems to be that in 1788 implementations based on 754, they'd be stored in the payload of a 754 NaN.
I am rather baffled by this. A decorated interval can have an arbitrary value as its interval part.
Suppose what I expect will be the commonest interval format: inf-sup with 754 binary64 bounds. Then a decorated nonempty interval [xlo,xhi], say, will be stored as
[(interval part) = (8 bytes for xlo) + (8 bytes for xhi)] + (decoration part).
Where is the NaN? I've always been assuming the decoration will be a separate byte, giving 17 bytes in all.
BTW, Nate: I have also found your notion of a "bare decoration" puzzling, since sometimes it seemed to be just a byte, and sometimes something stored in payload of a NaN within the interval part. Can you clarify?
Now we are getting close to the nitty-gritty, it's important we have a common understanding of these issues, so we can discuss alternatives intelligently.
John