code: public static boolean isNaN(
      final char k)
    {
      final int e = unpackGetExponentUnbiased(k);
      final int s = unpackGetSignificand(k);
      return (e == 16) && (s > 0);
    }
docs: @param k A packed {@code binary16} value
  
  @return {@code true} if the given packed {@code binary16} value is not a
  number ({@code NaN}).