In that specific case, how do you modify it? What function can you use. You dont know that a & b are numeric, so you can use arithmetic, you dont know that thei

In that specific case, how do you modify it? What function can you use. You dont know that a & b are numeric, so you can use arithmetic, you dont know that their strings, you actually have put zero constraints on the types of a and b, so there are almost no sufficiently generic functions you could apply to them. You could pass them to the "identity" function to "modify" them, but that's not really changing them. Just about the only thing you can do to match the types is construct a tuple. A (somewhat faulty analogy) is imagine a method that takes in two variable odds type Object and returns a tuple of Objects. You can call any instance method on the object class, and any static method, but can't reference any class variables. And you can do any casts to or from Object. There is almost nothing left you can do but return a tuple of them. The types constrained your implementation.