SICP 2.2 习题答案

最新推荐文章于 2025-11-30 23:27:53 发布

最新推荐文章于 2025-11-30 23:27:53 发布 · 214 阅读

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#Scheme #数据结构

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本文介绍了一种使用Scheme语言定义和操作几何对象的方法。通过定义make-point, make-segment等函数来创建点和线段，并实现了midpoint-segment函数用于获取线段中点。这些函数展示了如何利用Scheme的基本构造cons, car, cdr来处理几何数据。

cons对于数据结构来说是一个很强大的东西

(define (print-point p)
  (newline)
  (display "(")
  (display (x-point p))
  (display ",")
  (display (y-point p))
  (display ")"))

(define (make-point x y)
  (cons x y))

(define (x-point p)
  (car p))

(define (y-point p)
  (cdr p))

(define (make-segment start end)
  (cons start end))

(define (start-segment segment)
  (car segment))

(define (end-segment segment)
  (cdr segment))

(define (midpoint-segment segment)
  (cons (/ (+ (x-point (start-segment segment)) (x-point (end-segment segment))) 2)
        (/ (+ (y-point (start-segment segment)) (y-point (end-segment segment))) 2)))

(define p1 (make-point 1 2))
(define p2 (make-point 1 4))
(define s (make-segment p1 p2))

(x-point p1)
(y-point p1)
(print-point p1)
(print-point (midpoint-segment s))