Re: Absolute value of intervals

On Mon, Nov 02, 2009 at 11:22:00AM +0000, Jasen Betts wrote:
> On 2009-10-27, Sam Mason <sam(at)samason(dot)me(dot)uk> wrote:
> > On Tue, Oct 27, 2009 at 03:25:02PM +0000, Sam Mason wrote:
> >> If the absolute value of an interval was defined to strip out all the
> >> negation signs you'd get the "wrong" answers out.
> >
> > Oops, forgot another reason! For maths to work (n) and (-(-n)) should
> > evaluate to the same value. Inverting all the signs, as negation does,
> > will ensure that these semantics remain.

Hum, I'm not entirely sure what I was thinking when I wrote the above.
it's got nothing to do with taking absolute values!

> There not requrement in mathematics that
>
> z be a member of the set { abs(z) , -abs(z) }
>
> consider the case of z=sqrt(-1)

That said, I don't follow your point at all.

--
Sam http://samason.me.uk/