#ifndef _intstack_h_
#define _intstack_h_

#include <cstddef>

// Implements a stack of integers.
class IntStack {
private:
	// Stack node type.
	struct StackNode {
		StackNode(int d, StackNode *n) {
			data = d;
			next = n;
		}
		int data;
		StackNode *next;
	};
    
	// Head of the stack
	StackNode *head;

public:
	// Must make sure stack is empty at construct.
	IntStack() {
		head = NULL;
	}

	// Push onto the stack.
	void push(int i) {
		head = new StackNode(i, head);
	}

	// Remove from the stack.
	int pop();

	// Find out what's on the top.
	int top() {
		if(head == NULL)
			return 0;
		else
			return head->data;
	}

	// So, are we empty yet?
	bool isEmpty() {
		return head == NULL;
	}

	// Remove all memory from the stack.
	void clear();
};

#endif