* take. Courses are not associated with professors or meeting times,

 * those are in the realm of the Section and SectionMeeting.

 *

 * Iterating over this object will return CourseSlot objects, which

 * act exactly like most universities' idea of a course. However, some

 * universities have one Course and require students to take one

 * section from each of different categories of sections within in a

 * course. For example, at umich for any course which has a listing of

 * Sections of the type 'discussion' the student _must_ take one of

 * these 'discussion' sections in addition to, for example, a

 * 'lecture' Section.

 */

class Course implements IteratorAggregate

{

  private $name;	// String

  private $title;       // String

  private $sections;	// Array of sections, for __wakeup() to convert to CourseSlots.

  private $nsections;	// int, for __wakeup() to convert to CourseSlots.

  /**

   * \brief

   *   Other courses that this course depends on.

   *

   * Example: Many calvin courses depend on lab courses.

   */

  private $dependencies;

  /**

   * \brief

   *    Creates a class with the given name.

   *

   * When updating this function, update the call to ``new Course()''

   * in Schedule::findPossibilities(), Schedule::writeoutTables(), and

   * Schedule::courses_get().

   *

   * \param $course_id

   *    The identifier of the class. Ex., MATH-101 in

   *    MATH-101-A. Retrieved with Course::getName().

   * \param $title

   *    The human-friendly course title, such as 'Introduction to

   *    Algebra', or NULL.

   */

  public function __construct($course_id, $title = NULL)

  {

    $this->slots = array();

    $this->name = $course_id;

    $this->title = $title;

    $this->dependencies = array();

  }

  /**

   * \brief

   *   Adds an already-instantiated Section to this class.

   *

   * \param $section

   *   The Section to append to this Course.

   * \param $course_slot_id

   *   The string identifer of the CourseSlot to place the given

   *   Section into. Most schools will not specify this.

   */

  public function section_add(Section $section, $course_slot_id = 'default')

  {

    if (empty($this->slots[$course_slot_id]))

      $this->slots[$course_slot_id] = new CourseSlot($course_slot_id);

    $this->slots[$course_slot_id]->section_add($section);

  }

  /**

   * \brief

   *   Append a CourseSlot to this Course.

   *

   * If this course already contains a CourseSlot with the same

   * CourseSlot identifier as $course_slot, then the new CourseSlot

   * will replace the old one.

   *

   * \param $course_slot

   *   The CourseSlot to append.

   */

  public function course_slot_add(CourseSlot $course_slot)

  {

    $this->slots[$course_slot->id_get()] = $course_slot;

  }

  /**

   * \brief

   *   Required function to implement the IteratorAggregate interface.

   */

  public function getIterator()

  {

    return new ArrayIterator($this->slots);

  }

  /**

   * \brief

   *   Retrieve a section of this Course based on its letter.

   *

   * This function will automatically search CourseSlots for this

   * Section. Why? Because even though we support multiple