#include "itemtype.h"           // typedef for ItemType

#ifndef NULL                    // If NULL is not yet defined
#define NULL 0                  // define it
#endif

// The bool's that are returned by the methods take value 1 if the
// method succeeds and 0 otherwise (if there is overflow, underflow, etc.)

struct StackNode {
  ItemType item;
  StackNode * next;

  StackNode();
  StackNode(ItemType newitem, StackNode * newnext);
};

class Stack {
 public:
  Stack();
  ~Stack();
  bool Init();                 //(re-)Initializes the stack by emptying it
  bool IsEmpty();              //tests if stack is empty
  bool IsFull();               //tests if stack is full
  bool Push(ItemType item);    //pushes ItemType onto stack
  bool Pop(ItemType & item);   //pops stack and sets ItemType to popped value
 private:
  StackNode * list;                 //the linked list of items 
};