#ifndef __OPENGLPLAYGROUND_SINGLETON_HH__
#define __OPENGLPLAYGROUND_SINGLETON_HH__

#include <memory>
#include <mutex>

template<typename T>
class Singleton {
public:
  static T& getInstance() {
    call_once(instance_flag, init);
    return *instance;
  }

private:
  static std::unique_ptr<T> instance;
  static std::once_flag instance_flag;
  
  static void init() {
    instance.reset(new T{});
  }
};

#endif