On 12/19/09, Stefano Ferri <ferriste at gmail.com> wrote:
> I'm on Maxima 5.19.2 and I get the same result.
> With setcheck set to true I see:
>
> (%i10) sum(d(k),k,0,a);
> k SET TO g16510
> (%o10) a+1
>
> what does g16510 stand for?
Well, in general gnnnnn where nnnnn are some digits is an
automatically-generated symbol which is distinct from any
other existing symbol, a so-called gensym.
The summation code uses a gensym to make the summation
index a local variable.
I wrote that code, some years ago;
there is some confusion from time to time which is caused by
the peculiar evaluation policy of sum (different from other
Maxima functions). I've decided it's not worth the trouble;
next time someone modifies sum, I hope they get rid of its
special evaluation policy. It seemed like a good idea at the
time, but the accumulated experience since then indicates
otherwise.
> Moreover, doesn't Maxima knows about Gauss' formula?
>
> (%i11) sum(x,x,1,n);
> (%o11) 'sum(x,x,1,n)
>
> Maxima returns a noun form, instead of n*(n+1)/2
By default only trivial identities are applied.
Try: load(simplify_sum); simplify_sum('sum(whatever));
which applies several identities.
best
Robert Dodier