differential operators

Hi All, I'm new to GiNac. Is there a way to execute symbolic differentiation of expressions that includes differential operators ? e.g. suppose an expression ex F = u * dx*u When differentiate that expression F.diff(u) it should result in the expression dx*u - u*dx Regards Kai -- http://echempp.sourceforge.net Kai Ludwig Universität Tübingen Institut für Organische Chemie Auf der Morgenstelle 18 D-72076 Tübingen Tel.: 07071/29-73049 Mail: kai.ludwig@uni-tuebingen.de