srecord Frequency(double frequency) is Comparable<Frequency> {
  gettable double interval;
  
  double frequency aka get() { ret frequency; }
  
  // !customConstructor
  *(double *frequency) { interval = doubleRatio(1, frequency); }
  
  toString { ret format3(); }
  
  S format3() { ret format(3); }
  S format1() { ret format(1); }
  
  S format(int digits) { ret str(new Rendering(digits)); }
  
  record noeq Rendering(int digits) {
    double value = frequency;
    S unit = "Hz";
    
    swappable S formatValue() { ret formatDouble(value, digits); }
    
    run {
      while (abs(value) >= 1000) {
        value /= 1000;
        unit = "k" + unit;
      }
      unit = replacePrefixes(unit,
        "kkkk", "T",
        "kkk", "G",
        "kk", "M");
    }
    
    toString { run(); ret spaceCombine(formatValue(), unit); }
  }
  
  public int compareTo(Frequency f) {
    ret cmp(frequency, f.frequency);
  }
}