#include <iostream>

using namespace std;



// Snake
class Snake
{
private:
    class Segment; //Forward declare Segment
    
public:
    Snake(int x, int y): head{new Segment{x, y}}
    {}

    void print() const
    {
	Segment* current = head;
	while( current != nullptr )
	{
	    current -> print();
	    current = current -> get_next();
	}
	cout << "null";
    }

    void add(int x, int y)
    {
	//call the recursive function in first Segment
	head -> add(new Segment{x, y});
    }
    
private:
    Segment* head;
    class Segment //Segment is an internal class
    {             //Not visible outside of Snake
    public:       //User cannot create segments in main()
	Segment(int x, int y): x{x}, y{y}, next{nullptr}
	{}

	void add(Segment * s)
	{
	    //If there is no next segment
	    //add the new segment here
	    if (next == nullptr)
	    {
		next = s;
	    }
	    else // Otherwise call add in next segment
	    {
		next -> add(s);
	    }
	}

	void print() const
	{
	    cout << "(" << x << ", " << y << ") --> ";
	}

	Segment* get_next() const
	{
	    return next;
	}

    private:
	int x;
	int y;
	Segment* next; //Pointer to next segment
    };
};

int main()
{
    Snake snake{7, 7};
    snake.print();
    cout << "\n========" << endl;
    snake.add(7, 6);
    snake.print();
    cout << endl;
}