TF1* a = new TF1("aa","x");
TF1 *f = (TF1*)a->Clone("ff");
TF1 *g = (TF1*)a->Clone("gg");
TF1* h = new TF1("hh","ff+gg");
When calling the copy constructor, there is a problem with teh name of the
source function. Clone is taking care of it.
It only works for the “type A”, i.e. the one defined via string. For TFormulae defined via a function, you will need to provide a new function that does the combination.