#include <iostream>
 
class NotVirtual 
{
};
 
 
class Virtual 
{
public:
  virtual void foo() { }
};
 
 
template <typename VBase>
class Base : private VBase 
{
public:
  // The virtuality of foo() depends on its declaration
  // (if any) in the base class VBase
  void foo() 
  {
    std::cout << "Base::foo()" << '\n';
  }
};
 
 
template <typename V>
class Derived : public Base<V> 
{
public:
  void foo() 
  {
    std::cout << "Derived::foo()" << '\n';
  }
};
 
 
int main()
{
  Base<NotVirtual>* p1 = new Derived<NotVirtual>;
  p1->foo();  // calls Base::foo()
 
  Base<Virtual>* p2 = new Derived<Virtual>;
  p2->foo();  // calls Derived::foo()
}