anchor.diff:        "Range($start, $stop)" : "Range($start, $stop, $step)";
     }
   
  -  bool every(bool f(int)) {
  +  bool every(bool f(int e)) {
       for (int e in this) {
         if (f(e) == false) {
           return false;
  
positive.code:     return false;
    }
  
    void forEach(void f(int)) {
      for (int e in this) {
        f(e);
      }
    }
  
    List<int> filter(bool f(int)) {
      var l = new List<int>();
      for (int e in this) {
        if (f(e)) {
          l.add(e);
        }
      }
      return l;
    }
  
    List map(f(int)) {
      var l = new List();
      for (int e in this) {
        l.add(f(e));
      }
      return l;
    }
  
negative.code:     return true;
    }
  
    bool some(bool f(int e)) {
      for (int e in this) {
        if (f(e)) {
          return true;
  