docs: private static double[] reversed(double[] a) {
      // TODO: there doesn't appear to be a nicer version in Java, unfortunately.
      Arrays.sort(a);
      for(int i = 0, j = a.length - 1; i < j; i++, j--) {
        double tmp = a[i];
        a[i] = a[j];
        a[j] = tmp;
      }
      return a;
    }