sclass Average {
  double sum;
  double n;
  
  void add(double d) {
    ++n;
    sum += d;
  }
  
  void add(double d, double weight) {
    n += weight;
    sum += d*weight;
  }
  
  double get() {
    ret doubleRatio(sum, n);
  }
  
  toString { ret get() + " (n=" + n + ")"; }
  
  void clear {
    n = 0;
    sum = 0;
  }
}