code: private static String sourceForm(double v, char suffix) {
              if (Double.isNaN(v))
                  return "0" + suffix + "/0" + suffix;
              if (v == Double.POSITIVE_INFINITY)
                  return "1" + suffix + "/0" + suffix;
              if (v == Double.NEGATIVE_INFINITY)
                  return "-1" + suffix + "/0" + suffix;
              return v + (suffix == 'f' || suffix == 'F' ? "" + suffix : "");
          }
docs: where