/* Filename:  ArrStack.cpp

   Programmer:  Br. David Carlson

   Date:  August 8, 1998

   Modified:  April 23, 1999 to use an array-based implementation.

   Modified:  July 31, 2000 to use modern headers.

   This file implements the functions of the ArrStackClass found in
   ArrStack.h.
*/

#include "arrstack.h"


/* Given:  Nothing.
   Task:   This is a constructor. It creates and initializes a new stack
           to empty.
   Return: Nothing other than the newly created object.
*/
ArrStackClass::ArrStackClass(void)
   {
   Top = -1;
   }


/* Given:  Nothing (other than the implicit ArrStackClass object).
   Task:   To check whether this object is empty.
   Return: true if it is empty, false otherwise.
*/
bool ArrStackClass::Empty(void) const
   {
   if (Top < 0)
      return true;
   else
      return false;
   }


/* Given:  Item   A data item.
   Task:   To push item onto the stack (the implicit object).
   Return: Nothing directly, but the implicit object is modified.
*/
void ArrStackClass::Push(const ItemType & Item)
   {
   Top++;
   if (Top == StackMax)
      {
      cerr << "Error:  no room to push an item onto the stack" << endl;
      exit(1);
      }
   else
      Info[Top] = Item;  // assumes = works for ItemType
   }


/* Given:  Nothing.
   Task:   To pop the top item from the stack (the implicit object).
   Return: Item   The item popped from the stack.
*/
void ArrStackClass::Pop(ItemType & Item)
   {
   if (Top < 0)
      {
      cerr << "Error:  cannot pop an item from an empty stack" << endl;
      exit(1);
      }
   else
      {
      Item = Info[Top];   // assumes that = works on this type
      Top--;
      }
   }