On 12/11/08, Viktor T. Toth <vttoth at vttoth.com> wrote:
> (%i4) sum(i,i,q,n),simpsum;
> Is q positive, negative, or zero?
> neg;
> (%o4) (n^2+n)/2-(q^2+q)/2
> (%i5) %,q=-5,n=8;
> (%o5) 26
> Further, why does simpsum need asksign for this in the first place?
> Isn't the result given by simpsum for q>0, (n+1-q)*(n+q)/2, actually
> correct regardless of sign? That is, so long as q<=n?
Agreed, this is all strange. FWIW it appears that this strangeness
arises from FPOLYSUM in src/combin.lisp. Not sure what was
intended there, maybe someone can take a look.
Viktor, if you could make a bug report, that would be very helpful.
best
Robert Dodier