Implement a template function IsDerivedFrom() that takes class C and class P as template parameters. It should return true when class C is derived from class P and false otherwise.

true_if_derived.cpp

#include <iostream>
using namespace std;

class B {
};

class A : public B {
};

template<typename D, typename B>
class IsDerivedFromHelper {
  class No{
   
  };
  
  class Yes {
     No no[3];
  };
  
  static Yes Test(B*);
  static No Test(...);
public:
  enum {
    Is = sizeof(Test(static_cast<D*>(0))) == sizeof(Yes)
  };
};

template <class C, class P>
bool IsDerivedFrom(){
  return IsDerivedFromHelper<C, P>::Is;
}

// To execute C++, please define "int main()"
int main() {
  // true if A derived from B
  cout << IsDerivedFrom<A, B>();
  return 0;
}