// Fig. 26.5: Stack.cs
// Generic class Stack
using System;

class Stack< E >
{
   private int top; // location of the top element
   private E[] elements; // array that stores Stack elements

   // parameterless constructor creates a Stack of the default size
   public Stack() : this( 10 ) // default stack size
   {
      // empty constructor; calls constructor at line 18 to perform init
   } // end Stack constructor

   // constructor creates a Stack of the specified number of elements
   public Stack( int stackSize )
   {
      if ( stackSize > 0 ) // validate stackSize
         elements = new E[ stackSize ]; // create stackSize elements 
      else
         elements = new E[ 10 ]; // create 10 elements 

      top = -1; // Stack initially empty
   } // end Stack constructor

   // push element onto the Stack; if successful, return true
   // otherwise, throw FullStackException
   public void Push( E pushValue )
   {
      if ( top == elements.Length - 1 ) // Stack is full
         throw new FullStackException( String.Format(
            "Stack is full, cannot push {0}", pushValue ) );

      top++; // increment top
      elements[ top ] = pushValue; // place pushValue on Stack
   } // end method Push

   // return the top element if not empty
   // else throw EmptyStackException
   public E Pop()
   {
      if ( top == -1 ) // Stack is empty
         throw new EmptyStackException( "Stack is empty, cannot pop" );

      top--; // decrement top
      return elements[ top + 1 ]; // return top value
   } // emd method Pop
} // end class Stack

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 * (C) Copyright 1992-2006 by Deitel & Associates, Inc. and               *
 * Pearson Education, Inc. All Rights Reserved.                           *
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