Re: dependent and independent intervals, proposal to toss out text2interval. Was re: about emp (was: Motion 42:no)
On 2013-03-03 14:05:32 +0000, John Pryce wrote:
> For text2interval(s) where s is a string, here are some possible
> upper bounds.
> (a) No options. Only the mandatory syntax in 11.11.1 (of draft 7.0).
> (b) Permit the "enhanced syntax" in 11.11.1, but tighten up its
> specification to disallow many of the possibilities that have been
> discussed recently.
> (c) Permit arbitrary arithmetic expressions (of some defined syntax)
> within s, as in text2interval("0.1+pi") and other more exotic
> examples discussed.
>
> K.I.S.S. With respect, I think (c) is way beyond the bounds of
> reason, and the discussion of it has only served to confirm this.
IMHO, implementation-defined extensions should be allowed. As they
are extensions, they don't need to be specified.
The number (point) representation is not the only one involved.
For instance, an implementation may need to represent some specific
form of intervals...
> > (3) Other ways of denoting an interval (besides inf-sup and
> > mid-rad) may be provided.
[...]
> - (3) clearly opens "an arbitrary can of worms". So either delete
> it, or restrict to one or two specified alternatives, e.g. §6.4
> "Uncertain numbers" and/or §6.5 "Exact numbers" in Arnold Neumaier's
> Vienna proposal. (Richard, you can get this from the position papers
> on the P1788 web site.)
I disagree. Some alternate form may be useful, e.g. triplex, or a
sum of intervals (which could be seen as some form of generalization
of floating-point expansions to interval arithmetic, for instance).
And I repeat: they would just be extensions and would not have to be
specified by P1788.
--
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)