code: protected void shiftLeft(int start, int end)
    {
      for (int i = start; i < end; ++i) {
        positions[i] = positions[i + 1];
        bins[i] = bins[i + 1];
      }
    }
docs: Shifts the given range of histogram bins one slot to the left
  
  @param start index of the leftmost empty bin to shift into
  @param end   index of the last bin to shift left