persistable sclass PercentIncrease {
  settable double percentIncrease;
  
  *(double *percentIncrease) {}
  
  double get() { ret percentIncrease; }
  double asFactor() { ret 1+percentIncrease/100; }
  
  static PercentIncrease fromFactor(double factor) {
    ret new PercentIncrease((factor-1)*100);
  }
  
  toString { ret plusMinusFix(formatDouble_significant(percentIncrease, 4)) + "%"; }
  
  PercentIncrease combineWith(PercentIncrease i) {
    ret new PercentIncrease()
  }
}