functional-programming - 最小最大方案 coord.x0 y0 x1 y1

Question

;; makeRectangle -- constructor for 'rectangle

(define makeRectangle
  (lambda (x0 y0 x1 y1)
       (makeGraph 'rectangle
               (list (makePoint x0 y0)
                     (makePoint x1 y1)))))

(makeRectangle 3 2 1 7)必须返回(rectangle (point 1 7) (point 3 2)) ，我将获得相同的返回(makeRectangle 1 2 3 7)or (makeRectangle 1 7 3 2)，我必须使用：

min x0 x1 min y0 y1 
max x0 x1 max y0 y1

但我不知道该怎么做。你能帮我解决这个问题吗？提前致谢。

Answer 1

你的意思是这样的：

(define makeRectangle
  (lambda (x0 y0 x1 y1)
    (makeGraph 'rectangle
               (makePoint (min x0 x1) (max y0 y1))
               (makePoint (max x0 x1) (min y0 y1)))))

如

-> (makeRectangle 3 2 1 7)
'(rectangle (point 1 7) (point 3 2))

-> (makeRectangle 1 2 3 7) 
'(rectangle (point 1 7) (point 3 2))

-> (makeRectangle 1 7 3 2) 
'(rectangle (point 1 7) (point 3 2))

-> (makeRectangle 3 7 1 2)
'(rectangle (point 1 7) (point 3 2))