public boolean hasPrev() 
	{
		if (left.hasPrev())
			return true;
		else if (right.hasPrev())
			return true;
		else if (last_choice == null)
			return false;
		else if (last_choice == left && !rightBOF)
			return ((Comparable)left.current()).compareTo(right.current()) > 0;
		else if (last_choice == right && !leftBOF)
			return ((Comparable)right.current()).compareTo(left.current()) > 0;
		else return false;
	}