hi volker,
one more comment -- you wrote in part,
> I discovered Maxima to be a wonderful way for teaching a first
> programming language combined with a CAS. To me and my
> students it is both easy and powerful.
i find the maxima language to be rather pleasant for programming.
it is simple (which puts limits on what one can do, but for beginners
that is not a problem), and it inherits from lisp the "everything is an
expression" point of view.
while we're on the topic, some language features which seem worth
considering are lexical scope, closures, and a package system.
for what it's worth,
robert dodier