anchor.diff:      PointsComputer pointsComputer = new PointsComputer(pointStream.stream);
       ImportantPointsComputer importantPointsComputer = new ImportantPointsComputer(pointStream.stream); 
       PointDensityComputer pointDensityComputer = new PointDensityComputer(pointStream.stream);
  +    LengthUpFlatDownComputer lengthUpFlatDownComputer = new LengthUpFlatDownComputer(pointStream.stream);
       
       for (var iter = rawData.points.iterator; iter.moveNext();) {
         pointStream.add(iter.current) ;
  
positive.code:   num get difficulty => _difficulty ;
   
    num get pointDensity => _pointDensity ;
  }
  
  
negative.code:     this._points = pointsComputer.points;
      this._importantPoints = importantPointsComputer.importantPoints;
      this._pointDensity = pointDensityComputer.pointDensity;
      this._inclinationUp = lengthUpFlatDownComputer.inclinationUp;
      this._inclinationDown = lengthUpFlatDownComputer.inclinationDown;
      this._lengthUp = lengthUpFlatDownComputer.lengthUp ;
  