#include <exception>

template <typename T>
class stackNode {
  public:
    T data;
    stackNode<T> *next;

    stackNode(const T& el,stackNode<T> *below=nullptr) :
      data(el),next(below) {}
};

class stackEmptyException : public std::exception {
  public:
    stackEmptyException() noexcept
    {}

    const char* what() const { return "Attempt to pop empty stack."; }
};

template <typename T>
class stack {
  public:
    stack() : head(nullptr) {}
    stack(const stack<T>& other) = delete;
    stack(stack<T>&& other) = delete;
    ~stack() {
      while(head != nullptr) {
        stackNode<T> *toDelete = head;
        head = head->next;
        delete toDelete;
      }
    }

    stack<T>& operator=(const stack<T>& other) = delete;
    stack<T>& operator=(stack<T>&& other) = delete;

    bool isEmpty() const { return head == nullptr; }

    void push(const T& item) {
      head = new stackNode<T>(item,head);
    }

    const T& top() {
      if(this.isEmpty()) throw stackEmptyException();
      return head->data;
    }

    void pop() {
      if(this.isEmpty()) throw stackEmptyException();
      stackNode<T> *toDelete = head;
      head = head->next;
      delete toDelete;
    }

  private:
    stackNode<T> *head;
};