//
//   This file contains the C# code from Program 6.6 of
//   "Data Structures and Algorithms
//    with Object-Oriented Design Patterns in C#"
//   by Bruno R. Preiss.
//
//   Copyright (c) 2001--2002 by Bruno R. Preiss, P.Eng.  All rights reserved.
//
//   http://www.brpreiss.com/books/opus6/programs/pgm06_06.txt
//
public class StackAsArray : AbstractContainer, Stack
{
    protected object[] array;

    private class Enumerator : IEnumerator
    {
	StackAsArray stack;
	protected int position = -1;

	internal Enumerator(StackAsArray stack)
	    { this.stack = stack; }

	public bool MoveNext()
	{
	    if (++position == stack.count)
		position = -1;
	    return position >= 0;
	}

	public object Current
	{
	    get
	    {
		if (position < 0)
		    throw new InvalidOperationException();
		return stack.array[position];
	    }
	}

	public void Reset()
	    { position = -1; }
    }

    public override IEnumerator GetEnumerator()
	{ return new Enumerator(this); }
    // ...
}