#include <stdio.h>

const int null_pointer_reference = -1;

template<typename T>
class smart_ptr
{
public:
	T* operator->()	const {if(ptr) return ptr; throw null_pointer_reference;}

	T& operator*() const {if(ptr) return *ptr; throw null_pointer_reference;}
	
	smart_ptr():ptr(NULL) {}
	
	smart_ptr(T* p):ptr(p) {}
	
	~smart_ptr() {delete(ptr); ptr = NULL;}		

	smart_ptr& operator=(T* p) {delete(ptr); ptr = p; return *this;}

private:	
	smart_ptr& operator=(const smart_ptr& s) {}
	
	//smart_ptr(smart_ptr& s):ptr(NULL) {}	
protected:
	T* ptr;
};

class myclass
{
public:
	int a;
	int b;
	
	myclass() {printf("\n new myclass object created.");}
	~myclass() {printf("\n myclass object deleted.");}
};

//test1: one smart_ptr assgined twice
void test1()
{
	smart_ptr<myclass> pObj1 = new myclass;
	pObj1->a = 100;
	
	pObj1 = new myclass;
}

//test2: assigning one smart_ptr to another
void test2()
{
	smart_ptr<myclass> pObj1;
	pObj1 = new myclass;

	//enable the following to see the program crash
	//smart_ptr<myclass> pObj2 = pObj1;
	//pObj2 = pObj1;
}

//test3: using uninitialized pointer
void test3()
{
	try
	{
		smart_ptr<myclass> pObj1;
		pObj1->a = 100;
	}
	catch(int e)
	{
		if (e == null_pointer_reference)
			printf("\n null pointer referenced");
	}
}

//test4: constness
void test4()
{
	const smart_ptr<myclass> pObj1 = new myclass;
	
	pObj1->a = 100;
}

int main()
{
	printf("\ntest1");
	test1();
	
	printf("\ntest2");
	test2();	
	
	printf("\ntest3");
	test3();
	
	printf("\ntest4");
	test4();

	printf("\nend of program\n");

	return 0;
}