singleton

#include <iostream>
using namespace std;
class singleton
{
public:
  static singleton* Instance();
protected:
  singleton(){}
private:
  static singleton* _instance;
};
singleton* singleton::_instance = 0;
singleton* singleton::Instance()
{
  if (_instance == 0)
    {
      _instance = new singleton;
    }
  return _instance;
}
int main()
{
 singleton::Instance();
 return 0;
}