#include <iostream>
#include <complex>
using namespace std;

class Base
{
public:
  virtual void a(int x)  {  cout << "Base::a(int)" << endl;   }
  // overload the Base::a(int) function
  virtual void a(double x) {  cout << "Base::a(double)" << endl;  }
  virtual void b(int x)  {  cout << "Base::b(int)" << endl;   }
  void c(int x)      {  cout << "Base::c(int)" << endl;   }
};

class Derived : public Base
{
public:
  // redefine the Base::a() function
  void a(complex<double> x)  {  cout << "Derived::a(complex)" << endl;   }
  // override the Base::b(int) function
  void b(int x)        {  cout << "Derived::b(int)" << endl;     }
  // redefine the Base::c() function
  void c(int x)        {  cout << "Derived::c(int)" << endl;     }
};

int main()
{
  Base b;
  Derived d;
  Base* pb = new Derived;
  // ----------------------------------- //
  b.a(1.0);               // Base::a(double)
  d.a(1.0);               // Derived::a(complex)
  pb->a(1.0);              // Base::a(double), This is redefine the Base::a() function
  // pb->a(complex<double>(1.0, 2.0));  // clear the annotation and have a try
  // ----------------------------------- //
  b.b(10);                // Base::b(int)
  d.b(10);                // Derived::b(int)
  pb->b(10);               // Derived::b(int), This is the virtual function
  // ----------------------------------- //
  delete pb;

  return 0;
}