#ifndef stack_h
#define stack_h 1

template <class T> class stack
{
public:
    ~stack() { while (!empty()) pop(); } // NOT THREAD-SAFE!!!

    bool empty() const { return head == nullptr; } // FOR HOW LONG???

    void push(T t)
    {
        head = new node{head, t}; // LOCK-FREE???
    }

    T pop()
    {
        node *n = head;
        head = n->next; // UNDEFINED BEHAVIOR!!!
        T t = n->data;  // UNDEFINED BEHAVIOR!!!
        delete n;       // LOCK-FREE???
        return t;
    }

private:
    struct node
    {
        node *next = nullptr;
        T data;
    };

    node *head = nullptr;
};

#endif // stack_h