code: function(excludeWhole) {
  
        let n = this["n"];
        let d = this["d"];
        let str = this['s'] < C_ZERO ? "-" : "";
  
        if (d === C_ONE) {
          str += n;
        } else {
          let whole = n / d | C_ZERO;
          if (excludeWhole && whole > C_ZERO) {
            str += whole;
            str += " ";
            n %= d;
          }
  
          str += n;
          str += '/';
          str += d;
        }
        return str;
      }
docs: Returns a string-fraction representation of a Fraction object
  
  Ex: new Fraction("1.'3'").toFraction() => "4 1/3"