// *********************************************************
// Implementation file StackA.cpp for the ADT stack.
// Array-based implementation.
// *********************************************************
#include "StackA.h"  // Stack class specification file

Stack::Stack(): top(-1)
{
}  // end default constructor

Stack::~Stack()
{
  popAll();
}

bool Stack::isEmpty() const
{
   return top < 0;
}  // end isEmpty

void Stack::push(Object* newItem) throw(StackException)
{
// if stack has no more room for another item
   if (top >= MAX_STACK-1)
      throw StackException("StackException: stack full on push");
   else
   {  ++top;
      items[top] = newItem;
   }  // end if
}  // end push

Object* Stack::pop() throw(StackException)
{
   if (isEmpty())
      throw StackException("StackException: stack empty on pop");
   else {
      Object* stackTop=items[top];
      --top;     // stack is not empty; pop top
      return stackTop;
   }
}  // end pop

void Stack::popAll()
{
   while (!isEmpty())
   {  // stack is not empty; deallocate object at top
      delete items[top];
      --top;     // pop top
   }  // end if
}  // end popAll

const Object* Stack::peek() const throw(StackException)
{
   if (isEmpty())
      throw StackException("StackException: stack empty on getTop");
   else
      // stack is not empty; retrieve top
      return items[top];
}  // end peek
// End of implementation file.