#include<iostream>

using namespace std;


class Singleton
{
	public:
		static Singleton* InstancePointer();
		static Singleton& InstanceReference();
		void Show();
		void Increment();
	private:
		Singleton();
		static Singleton* m_Instance;
		
		// other data members
		int m_x;

};

//must initialize static members outside of class definition
Singleton* Singleton::m_Instance = NULL;

Singleton::Singleton()
{
	m_x = 0;
}

Singleton* Singleton::InstancePointer()
{
	if (m_Instance == NULL)
	{
		m_Instance = new Singleton;
	}
	return m_Instance;
}

Singleton& Singleton::InstanceReference()
{
	if (m_Instance == NULL)
	{
		m_Instance = new Singleton;
	}
	return *m_Instance;
}


void Singleton::Show()
{
	cout << "Singleton m_x = " << m_x << endl;
}

void Singleton::Increment()
{
	m_x++;
}

void main()
{
	Singleton* s1 = Singleton::InstancePointer();
	Singleton* s2 = Singleton::InstancePointer();
	Singleton& s3 = Singleton::InstanceReference();

	s1->Show();
	s2->Show();
	s3.Show();

	s1->Increment();
	s2->Show();
	s3.Show();

	Singleton::InstanceReference().Increment();
	Singleton::InstanceReference().Show();

	s1->Show();

	//which is safer returing a reference or pointer
	//delete s2;


}