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