/**
 * Collections of elements not supporting iteration.
 */
public interface Linear
{
  // +-----------+-----------------------------------------------
  // | Accessors |
  // +-----------+
  
  /**
   * Determine if the collection is full (in which case no more
   * elements can be added).
   * Precondition: The collection is initialized.
   * Postcondition: Returns true if the collection is full, and
   *   false otherwise.
   */
  public boolean isFull();
  
  /**
   * Determine if the collection is empty (in which case no elements
   * can be deleted).
   * Precondition: The collection is initialized.
   * Postcondition: Returns true if the collection is empty, and
   *  false otherwise.
   */
  public boolean isEmpty();
  
  /**
   * Get the next element to be returned in the collection
   * Precondition: The collection is initialized and nonempty.
   * Postcondition: An element is returned.  The particular element
   *   returned is determined by the policies of the linear structure.
   */
  public Object next();
  
  // +-----------+-----------------------------------------------
  // | Modifiers |
  // +-----------+
  
  /**
   * Add an element to the collection.
   * Precondition: The collection is intialized and is not full.
   * Postcondition: The element is added to the collection.
   * Postcondition: The collection grows by one element.
   */
   public void add(Object elt);
   
   /**
    * Delete an element from the collection.
    * Precondition: The collection is initialized and nonempty.
    * Postcondition: An element is deleted from the collection.  The
    *   particular element deleted is determined by the policies of
    *   the linear structure.
    * Postcondition: Returns the element deleted.
    * Postcondition: The collection shrinks by one element.
    */
   public Object delete();
   
} // interface Linear