/** @file StackP.h
 * Stack implementation using pointer based lists
 */

#include <stdexcept>
#include <string>
using namespace std;

typedef char StackItemType;

/*
 * A user-defined exception class for the Stack ADT
 */
class StackException : public logic_error
{
public:
   StackException(const string& message = "")
      : logic_error(message.c_str())
   {}
};

/*
 * ADT stack - Pointer-based implementation.
 */
class Stack
{
public:
  // Constructors and destructor:
  /** Default constructor. */
  Stack();

  /** Copy constructor.
   * @param aStack The stack to copy. */
  Stack(const Stack& aStack);
  
  /** Destructor. */
  ~Stack();

  // Stack operations:
  bool isEmpty() const;
  void push(const StackItemType& newItem) throw(StackException);
  void pop() throw(StackException);
  void pop(StackItemType& stackTop) throw(StackException);
  void getTop(StackItemType& stackTop) const
    throw(StackException);
  
private:
  /** A node on the stack. */
  struct StackNode
  {
    /** A data item on the stack. */
    StackItemType item;
    /** Pointer to next node.     */
    StackNode    *next;
  }; // end StackNode
  
  /** Pointer to first node in the stack. */
  StackNode *topPtr;
};