Level 3 representation of 754-conforming inf-sup intervals (was: motioin43 amended)
On 2013-04-24 18:45:23 -0700, Dmitry Nadezhin wrote:
> Vincent,
>
> > > I assume that the use of -0 has been discussed and rejected some
> > > time previously by 1788 committee.
> >
> > No, it was just decided that all intervals are closed. Then how
> > they are represented (Level 3) or encoded (Level 4) is currently
> > unspecified.
>
> It is not specified how they are represented internally. Section
> 14.3 of draft 7.1 says that representation of 0 in interchange
> format is +0 .
AFAIK, there has never been a vote on this point. If a choice is
made, I think that -0 for the lower bound would be the most natural
one as it would be the consequence of using the roundTowardNegative
rounding-direction attribute for its computation.
And, IMHO, for decimal formats, the cohort should be unspecified.
I don't see the point for an implementation to define the cohort,
as the cohort doesn't affect the values (except for particular
operations whose goal is to deal with it). In practice, it will
depend on the algorithms used by the implementation.
--
Vincent Lefèvre <vincent@xxxxxxxxxx> - Web: <http://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <http://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)