#include <iostream>
using namespace std;
 
class base
{
public:
  virtual base& downcast()
  {
  	cout << "Downcast-base" << endl;
    return *this;
  }
};
 
class derived: public base
{
public:
  virtual derived& downcast()
  {
  	cout << "Downcast-derived" << endl;
    return *this;
  }
};
 
void foo(const base& a)
{
  cout << "base" << endl;
}
 
void foo(const derived& a)
{
  cout << "derived" << endl;
}
 
int main()
{
  base* ptr1 = new(base);
  base* ptr2 = new(derived);
 
  foo(ptr1->downcast());
  foo(ptr2->downcast());
 
  return 0;
}

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