Thanks for your tips.
I hesitate from the first solution, because Maxima would have to compute everything twice. I already thought of the second solution (as soon as I discovered "grind"), but did not find the time to try it. It requires some rearrangements in the code, and the Maxima code is already quite involved due to the preprocessor stuff I am doing, and the postprocessing necessary to remove the output labels and catch Maxima errors.
Thanks in any case. I would love to keep the Maxima community informed about the things I do with their child.
May I add a few questions:
(1) Can I tell Maxima not to print (%o...)? It does not make sense in my notebook environment.
(2) Can I interrupt Maxima computations via pipes? I did a lot of investigation on that point, but did not find a way to achieve it.
(3) How can I get Maxima to accept my style of matrices [1,2;3,4] with rows separated by semicolons? This can be solved by a text preprocessor, but might be easy in Maxima itself.
Yours,
R.G.