The following code example is taken from the book
C++ Templates - The Complete Guide, 2nd Edition
by David Vandevoorde, Nicolai M. Josuttis, and Douglas Gregor,
Addison-Wesley, 2017
© Copyright David Vandevoorde, Nicolai M. Josuttis, Douglas Gregor 2017
template<typename R, typename... Args>
class FunctorBridge
{
public:
virtual ~FunctorBridge() {
}
virtual FunctorBridge* clone() const = 0;
virtual R invoke(Args... args) const = 0;
};