package rebelsky.list;

/**
 * Simple cursors for array-based simple lists.
 *
 * @author CSC152 2004F
 */
class ArrayBasedSimpleCursor
	implements SimpleCursor
{
// +--------+------------------------------------------------------------
// | Fields |
// +--------+

	/**
	 * The position in the array.
	 */
	int p;
	
	/**
	 * The list that we iterate.
	 */
	ArrayBasedSimpleList list;

// +--------------+------------------------------------------------------
// | Constructors |
// +--------------+

	/**
	 * Construct the cursor.
	 */
	public ArrayBasedSimpleCursor(ArrayBasedSimpleList _list)
	{
		this.p = 0;
		this.list = _list;
	} // ArrayBasedSimpleCursor
	
// +---------+-----------------------------------------------------------
// | Methods |
// +---------+

	/**
	 * Get a value not yet visited by this cursor.  See
	 * interface for more details.
	 */
	public Object next()
		throws NoSuchPosition
	{
		// Make sure that it's a valid position.
		if (!this.hasNext())
			throw new NoSuchPosition("Can't get position " + this.p + " in an " + this.list.n + " element list ");
		// Look it up in the array.
		Object tmp = this.list.contents[this.p];
		// Add one to p to move to the next place.
		++this.p;
		// That's it.
		return tmp;
	} // next()

	/**
	 * Determine whether or not unvisited elements remain.
	 * See interface for more details.
	 */
	public boolean hasNext()
	{
		return this.p < this.list.n;
	} // hasNext()
} // class ArrayBasedSimpleCursor