On 9/7/10 10:40 PM, Viktor T. Toth wrote:
> Right now (testing with 5.21.0 and the current CVS), we have
>
> (%i3) limit(2/x-1/x,x,0);
> (%o3) infinity
>
> but
>
> (%i6) limit(2/x,x,0)-limit(1/x,x,0);
> (%o6) 0
>
> That just does not smell right.
>
> Shouldn't we have
>
> inf + inf = inf (NOT 2 inf),
> inf - inf = und (NOT 0),
> minf + minf = minf (NOT 2 minf),
> minf - minf = und,
> inf - minf = inf,
> minf - inf = minf,
> infinity + inf = infinity + minf = infinity + infinity = und,
> infinity - inf = infinity - minf = infinity - infinity = und?
I think these are all known bugs. I did some work on this but never
finished it. I think Dieter has also done some work on this.
Shouldn't infinity + infinity = infinity? But I guess I can see und
being a possible valid answer too.
Ray