Maxima doesn't assume ommutativity? (bug?)

Good day,

The example I gave was too simple. Yes, a*b-b*a does simplifies to 
zero... but see the slightly more challenging problem below...

Do you feel I should report this as a bug or am I being silly??? Please, 
someone, do a sanity check on me! It seems to me that Maxima doesn't 
assume commutativity!!!! (why???)



[lemire@romeo lemire]$ maxima
GCL (GNU Common Lisp)  Version(2.5.0) jeu jan 31 23:03:22 EST 2002
Licensed under GNU Library General Public License
Contains Enhancements by W. Schelter
Maxima 5.6 jeu jan 31 23:03:13 EST 2002 (with enhancements by W. Schelter).
Licensed under the GNU Public License (see file COPYING)
(C1) expand((-A^3*a/64+a*A^3/64));

                                      3    3
                                   a A    A  a
(D1)                              ---- - ----
                                    64     64
(C2) scsimp(D1);

                                      3    3
                                   a A    A  a
(D2)                              ---- - ----
                                    64     64
(C3)


This type of bug crept up on my as I was doing some "real" research 
using Maxima. I had a conjecture that such polynomial and such other 
polynomial would simplify in such a way that... (skip details)... but I 
spent (wasted) a day with very complicated formulas until a realized 
that Maxima didn't assume commutativity!!! So that even though I 
strongly suspected that things would greatly simplify, they apparently 
did not!

Of course, here I give a rather simple examples, but it happened to me 
several times over the last few weeks, involving various complicated 
expressions. This one was the simplest I could find.

This problem seems to happen systematically, but is somewhat random at 
the same time (that is, I can't tell from the expression whether this 
bug will happen... but once it happens for a certain expression, if I 
have this expression with other terms, the problem with happen! Hence, 
it is systematical...)

I've recently upgraded my lisp. It didn't fix the problem for me.

I have
Linux  2.4.2-2 with a 686

Maxima built from cvs using latest lisp (from cvs). The problem happened 
to me on the maxima RPM though.

I can't believe I would be the first one to notice this problem???

-- 
Daniel Lemire, Ph.D.

http://www.ondelette.com/