* <p>Technically speaking, this is equivalent to {@code Math.abs(a - b) <= tolerance ||
   * Double.valueOf(a).equals(Double.valueOf(b))}.
   *
   * <p>Notable special cases include:
   *
   * <ul>
   *   <li>All NaNs are fuzzily equal.
   *   <li>If {@code a == b}, then {@code a} and {@code b} are always fuzzily equal.
   *   <li>Positive and negative zero are always fuzzily equal.