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Re: Bare decorations (was ...level 2 datums)



> Date: Tue, 2 Nov 2010 09:53:39 +0100
> From: Vincent Lefevre <vincent@xxxxxxxxxx>
> To: stds-1788 <stds-1788@xxxxxxxxxxxxxxxxx>
> Subject: Re: Bare decorations (was ...level 2 datums)
> 
> On 2010-10-25 19:08:09 -0500, Nate Hayes wrote:
> > >(a) It doesn't cover a mix of operands, such as (bare interval) + (bare
> > >decoration).
> > 
> > This is covered by 2.3 that says any operation involving a bare decoration
> > must always result in a bare decoration. In IEEE 754, this is analagous to
> > how any arithmetic operation involving a NaN must return a NaN, i.e.,
> >    2 + NaN = NaN
> > and not something like
> >    2 + NaN = 2
> > which would cause serious problems.
> 
> I think you should forget this analogy, because it is incorrect.
> For instance, hypot(+inf,qNaN) gives +inf, not qNaN (Section 9.2.1).
> 
> -- 
> Vincent Lefèvre <vincent@xxxxxxxxxx> - Web: <http://www.vinc17.net/>

	Vincent,

	While I do not agree with this approach to bare
	intervals & bare decorations, I think Nate is
	generally going in the right direction to treat
	bare decorations as a flavor of NaI that is
	generally NaI preserving.

	You are also correct in that there will be some
	minor exceptions.  Some hypot cases are one.
	Some selection functions are another.  We may
	have max([al,au],<bare_decoration>) want to be
	the interval or we may want it to be [al,+inf].
	Just as we may want max(interval,empty) to be
	the interval.  I'm not sure yet.  There may be
	some subtlties I'm missing.

	I don't really want to start a discussion on
	these corner cases.  I'm just thinking out loud.

	We have far more important things to decide first.

	Yours,

				Dan