anchor.diff:  
         // skip showing empty weeks
         for (int d = 0, w0 = 0; d < 7; d++) {
  -        if (_calMtable.contains([w][d])) w0++;
  +        if (_calMtable[w][d] != 0)  w0++;
           if (w0 == 0) continue;
         }
   
  
positive.code: 
      for (int i = 0, w = 0; i < mdays; i++) {
        if (i != 0 && wd == 0) w++;
        _calMtable[w][wd] = i + 1;
        wd = (wd + 1) % 7;
      }
    }
  
negative.code:   final _random = new Random();
    int _next(int min, int max) => min + _random.nextInt(max - min);
    List _calWtable = new List();
    List<List<int>> _calMtable = new List<List<int>>();
  
    var _pool;
    final String _calTable = "lwc";
  