C#使用自己寫的海龜繪圖類繪製遞迴分型樹

paython裡有個庫，叫turtle，俗稱海龜作圖。自己看《程式設計師的數學》時，在遞迴章節看了用海龜繪圖畫遞迴樹，我想用C#在winform上用gdi+去實現，我卻沒有在網上找到有適合C#語言的類似的庫，我就自己簡單寫了一個海龜作圖幫助類，實現了上圖的圖案。程式碼如下：

 public class TurtleHelper : IDisposable
    {
        private Graphics g;
        private int len = 30;
        private int curDegree = 0;
        public int degree = 15;
        private Point curPos;
        private Pen pen =null;

        private Stack<Point> stPoints;


        public TurtleHelper(Graphics g, Point basePoint)
        {
            this.g = g;
            this.curPos = basePoint;
            pen = Pens.Black;
            stPoints = new Stack<Point>();
           
        }

        public void left()
        {
            this.curDegree += this.degree;
        }

        public void right()
        {
            this.curDegree -= this.degree;
        }

        public void forward()
        {
            stPoints.Push(curPos);
            Point nextPoint = default;
            nextPoint.X =(int) (curPos.X - Math.Sin(curDegree/180.0 * Math.PI) * this.len);
            nextPoint.Y = (int)(curPos.Y - Math.Cos(curDegree / 180.0 * Math.PI) * this.len);
            this.g.DrawLine(pen, curPos, nextPoint);
            curPos = nextPoint;
           
        }
        public void back()
        {
            if(stPoints.Count>0)
            {
                var p = stPoints.Pop();
                curPos = p;
            }
        }

        public void Dispose()
        {
            g.Dispose();
        }


        
    }

三角函式，度數需要換算成弧度值，以上實現了海龜作圖的基本方法，然後在窗體畫遞迴樹的程式碼：

TurtleHelper helper = null;

        protected override void OnPaint(PaintEventArgs e)
        {
            base.OnPaint(e);
            helper = new TurtleHelper(e.Graphics, new Point(350, 350));
            drawtree(7);
            helper.Dispose();
        }

        public void drawtree(int n)
        {
            if(n==0||helper==null)
            {
               return;
            }
            else
            {
                helper.left();
                helper.forward();
                drawtree(n - 1);
                helper.back();
                helper.right();
                helper.right();
                helper.forward();
                drawtree(n - 1);
                helper.back();
                helper.left();
            }
        }