Re: motion elementary functions
> Date: Mon, 19 Oct 2009 08:48:18 +0200
> From: "J. Wolff v. Gudenberg" <wolff@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
> To: John Pryce <j.d.pryce@xxxxxxxxxxxx>
> CC: Dan Zuras Intervals <intervals08@xxxxxxxxxxxxxx>,
> stds-1788@xxxxxxxxxxxxxxxxx
> Subject: Re: motion elementary functions
>
> John,
> I completely agree. That is the reason why I chose pow and pown as
> mandatory functions.
> Juergen
>
> John Pryce schrieb:
> > P1788, Dan
> >
> > . . .
> >
> > So, I agree 100% with Dan's analysis, and description of a possible
> > all-singing-all-dancing power function. But on reflection I don't think
> > the "negative x to a rational power" aspect is of benefit to any
> > interval application I can envisage. I think the Vienna proposal 3.12
> > has it exactly right with its two functions
> >> The binary operation pow,
> >> where a pow b is defined for nonnegative a and real b,
> >> provided that b is positive when a is zero
> >> must be complemented by a binary operation intpow,
> >> where a intpow p is defined for real a and integer p,
> >> provided that p is nonnegative when a is zero.
> >
> > That is what I expect to vote for.
> >
> > John
Gentlemen,
Both are reasonable functions to demand we have lying
around for use by 1788.
But both are Real functions of Real or integer powers.
In 1788 we are in the business of defining interval
functions of interval arguments.
It was that issue I was trying to address & that about
which my argument was made.
Demand any useful set of power functions you feel is
necessary to aid in the development of an interval
library.
But I would still like to hope that we can get past
the mistakes of 754 & come to some agreement on a
single x^y in the domain & range of the intervals.
It is possible, I believe.
In a way that:
is mathematically correct,
is as general as possible, &
was NOT possible for floating-point.
Dan