[GiNaC-list] Question regarding symbolic differentiation

Hello, i have a question regarding symbolic differentiation with GiNAC. Here is what i am trying to do: I have to variables a(t) and b(t), both are dependent from time (t). Suppose, this two variables are multiplied liked this: a(t) * b(t) Is it possible to derive this expression (a(t)*b(t)) according time with ginac. The only function i found in the manual is usefull for partial derivation, which does not help me here. Here is some example code: symbol a("a"), b("b"); // <-- how to tell ginac that variable a and b is dependant from variable t expression f = a*b; std::cout << f.diff(t,1) << std::endl; Many thanks in advance and best regards Martin Ettl