docs: public static void drawLine(int x0, int y0, int x1, int y1, PlotOperator plot)
      {
          if (x0 > x1)
          {
              drawLine(x1, y1, x0, y0, plot);
          }
          else
          {
              if (y0 > y1)
              {
                  drawLine(x0, -y0, x1, -y1, (x, y) -> plot.plot(x, -y));
              }
              else
              {
                  drawLine1(x0, y0, x1, y1, plot);    // ok to go ahead
              }
          }
      }