Re: Bare decorations (was ...level 2 datums)
Replying to me, Nate Hayes wrote:
> How about using quiet NaNs instead but just reserving a special bit
> to distinguish between empty set and bare decorations?
Unreliable NaN propagation kills any attempt to put essential meaning
into any QNaN payload. The only manageable use is for debugging hints,
where one tolerates getting one of several possible hints at the end.
(One other is for SNaNs when they communicate with an exception handler.)
> I think if I understand correctly you are suggesting something like:
> ÝNaN,x¨
> where "x" is some non-NaN IEEE 754 bit-pattern that carries the payload
> of decorations.
Almost. It doesn't have to be a 754 bit pattern; indeed, if one wants
to perform boolean operations on the bits it's better to use a Uint.
On platforms where this has to live in FP registers that are more than
just bit buckets this might not work, so the choice will have to be up
to the platform-specific aspects of the implementation.
Michel.
---Sent: 2010-10-07 01:22:13 UTC