//////////////////////////////
// MT1Q4.cpp - Base clone

#include <iostream>
#include <exception>

template <typename T>
class B
{
public:
  B() : msg("a B message") {}
  virtual ~B() {}
  B<T>* clone()
  { 
    T* pT = dynamic_cast<T*>(this); 
    if(!pT)
      throw std::bad_cast();
    return new T(*pT); 
  }
  virtual void say() const
  { 
    std::cout << "\n  " << typeid(*this).name(); 
  }
private:
  std::string msg;
};

class D : public B<D>
{
public:
  D(std::string msg) : _msg(msg) {}
  virtual void say() const
  {
    B<D>::say();
    std::cout << "\n  my string value - " << _msg.c_str();
  }
private:
  std::string _msg;
};

void main()
{
  B<D> b;
  b.say();
  D d("hi from a D");
  d.say();
  std::cout << "\n  calling clone operation:";
  B<D>* pB = d.clone();
  pB->say();
  std::cout << "\n  calling clone operation polymorphically:";
  pB = &d;
  pB = pB->clone();
  pB->say();
  std::cout << "\n\n";
}