/**
 * Base interface for priority queue implementations for doubles. Throw
 * exceptions as appropriate.
 */
public interface PriorityQueue {
    /**
     * Returns true if priority queue has no elements
     * 
     * @return true if the priority queue has no elements
     */
    public boolean isEmpty();

    /**
     * Returns the number of elements in this priority queue.
     * 
     * @return the number of elements in this priority queue.
     */
    public int size();

    /**
     * Returns the minimum element in the priority queue
     * 
     * @return the minimum element
     * @throws EmptyPQException
     *             if priority queue contains no elements
     */
    public double findMin();

    /**
     * Inserts a new element into the priority queue. Duplicate values ARE
     * allowed.
     * 
     * @param x
     *            element to be inserted into the priority queue.
     */
    public void insert(double x);

    /**
     * Removes and returns the minimum element from the priority queue.
     * 
     * @return the minimum element
     * @throws EmptyPQException
     *             if priority queue contains no elements
     */
    public double deleteMin();

    /**
     * Resets the priority queue to appear as not containing any elements.
     */
    public void makeEmpty();

}