}
    Range<C> span = span().canonical(domain);
    if (!span.hasLowerBound()) {
      // according to the spec of canonical, neither this ImmutableRangeSet nor
      // the range have a lower bound
      throw new IllegalArgumentException(
          "Neither the DiscreteDomain nor this range set are bounded below");
    } else if (!span.hasUpperBound()) {
      try {
        domain.maxValue();
      } catch (NoSuchElementException e) {

   *       equivalent(x, z)} is also true (<i>transitive</i> property)
   * </ul>
   *
   * <p>Note that all calls to {@code equivalent(x, y)} are expected to return the same result as
   * long as neither {@code x} nor {@code y} is modified.
   */
  public final boolean equivalent(@CheckForNull T a, @CheckForNull T b) {
    if (a == b) {
      return true;
    }
    if (a == null || b == null) {
      return false;
    }

   * PeekingIterator#remove()}.
   *
   * <p>Note: If the given iterator is already a {@code PeekingIterator}, it <i>might</i> be
   * returned to the caller, although this is neither guaranteed to occur nor required to be
   * consistent. For example, this method <i>might</i> choose to pass through recognized
   * implementations of {@code PeekingIterator} when the behavior of the implementation is known to