deque-blog/NVI.hpp

## NVI.hpp
class Interface
{
public:
    //...
    std::unique_ptr<Interface> clone()
    {
        return std::unique_ptr<Interface>(cloneImpl());
    }

protected:
    virtual Interface* cloneImpl() const = 0;
};
	class Interface
	{
	public:
	//...
	std::unique_ptr<Interface> clone()
	{
	return std::unique_ptr<Interface>(cloneImpl());
	}

	protected:
	virtual Interface* cloneImpl() const = 0;
	};