anchor.diff:      var _value, type;
   
       $PyNum(value) {
  -        type = $getType(value);
  -
  -        switch (type) {
  +        switch ($getType(value)) {
               case 6:
                   _value = value;
                   break;
  
positive.code:             default:
                  throw "Invalid input for num conversion";
          }
      }
  
      value() => _value;
  
negative.code:     final _stop, _step;
  
      $RangeIterator(pos, stop, step) : _stop = stop, _pos = pos - step, _step = step;
      get current => _pos;
  
      bool moveNext() {
  