/*
 * Stack ADT implementation using an array. The size of the array is a
 * constant. The type of the elements of the array is also a typedef
 */

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

const int MAX_STACK = 1000;
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())
   {}
};


/** @class Stack
 * ADT stack - Array-based implementation.
 */
class Stack
{
public:
  // constructors and destructor:
  /** Default constructor. */
  Stack();
  // copy constructor and destructor are
  // supplied by the compiler
  
  // stack operations:
  /** Determines whether this stack is empty.
   * @pre None.
   * @post None.
   * @return True if this stack is empty; otherwise returns
   *         false. */
  bool isEmpty() const;
  
  /** Adds an item to the top of this stack.
   * @pre newItem is the item to be added.
   * @post If the insertion is successful, newItem is on the top
   *       of this stack.
   * @param newItem  The given StackItemType.
   * @throw StackException If the item cannot be placed on this
   *        stack. */
  void push(const StackItemType& newItem) throw(StackException);
  
  /** Removes the top of this stack.
   * @pre None.
   * @post If this stack is not empty, the item that was added most
   *       recently is removed. However, if this stack is empty,
   *       deletion is impossible.
   * @throw StackException If this stack is empty. */
  void pop() throw(StackException);
  
  /** Retrieves and removes the top of this stack.
   * @pre None.
   * @post If this stack is not empty, stackTop contains the item
   *       that was added most recently and the item is
   *       removed. However, if this stack is empty, deletion is
   *       impossible and stackTop is unchanged.
   * @throw StackException If this stack is empty. */
  void pop(StackItemType& stackTop) throw(StackException);
  
  /** Retrieves the top of this stack.
   * @pre None.
   * @post If this stack is not empty, stackTop contains the item
   *       that was added most recently. However, if this stack is
   *       empty, the operation fails and stackTop is
   *       unchanged. This stack is unchanged.
   * @throw StackException If this stack is empty. */
  void getTop(StackItemType& stackTop) const
    throw(StackException);
  
private:
  /** Array of stack items */
  StackItemType items[MAX_STACK];
  /** Index to top of stack */
  int           top;
};