Exercise 2.50 · 习题

Exercise 2.50: Define the transformation

flip-horiz, which flips painters horizontally, and transformations that

rotate painters counterclockwise by 180 degrees and 270 degrees.

练习 2.50：定义变换 flip-horiz，它将画家水平翻转；以及将画家逆时针旋转 180 度和 270 度的变换。