Nicolas,
> I would like to call Maxima from the underlying Lisp for communicating with
> a user. Therefore, I am interested in Lisp functions for writing data in
> 2d-format to a stream or string, and functions for evaluating a string
> containing a mathematical expression.
About evaluating a string, the eval_string add-on package has
parse_string and eval_string.
See comments in share/contrib/eval_string.lisp for more info.
e.g.
load (eval_string);
parse_string ("expand ((a + b) ^ 3)");
eval_string ("expand ((a + b) ^ 3)");
> P.S.: Is it possible to change the email address from which I am posting
> without a new subscription?
Theoretically http://math.utexas.edu/mailman/listinfo/maxima
can help you change your address. See "Unsubscribe or edit options"
at the bottom of the page.
Robert