package rebelsky.list;

/**
 * Things that indicate positions in a list and can move.  Cursors
 * start at the front of the list.
 *
 * @author CSC152 2004F
 */
public interface Cursor
	extends SimpleCursor
{
	/**
	 * Reset the cursor to the front of the list.
	 */
	public void toFront();

	/**
	 * Reset the cursor to the rear of the list.
	 */
	public void toRear();

	/**
	 * Determine if the cursor is still valid.
	 */
	public boolean isValid();

	/**
	 * Get the value "under" the cursor.
	 */
	public Object get();

	/**
	 * Advance the cursor to the next object.  Return that object.
	 *
	 * @pre
	 *   Must not be at the rear of the list.
	 */
	public Object next();

	/** 
	 * Retreat the cursor to the previous object and return that
	 * object.
	 *
	 * @pre
	 *   Must not be at the front of the ist.
	 */
	public Object prev();

	/*
	 * Determine if the cursor has any previous elements.
	 */
	public boolean hasPrev();

	/**
	 * Determine if the cursor has any remaining elements.
	 */
	public boolean hasNext();

} // interface Cursor