sicp 习题 2.21 ~ 2.25

最新推荐文章于 2019-08-02 08:23:56 发布

最新推荐文章于 2019-08-02 08:23:56 发布 · 247 阅读

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本文提供了多个Scheme语言编程示例，包括定义平方函数、处理列表元素的递归与迭代方法、遍历列表等实用技巧，有助于理解函数式编程的核心概念。

2.21


(define nil '())

(define (square x)
  (* x x))

(define (square-list items)
  (if (null? items)
      nil
      (cons (square (car items)) (square-list (cdr items)))))

(define (square-list-map items)
  (map (lambda (x) (square x)) items))

(square-list (list 1 2 3 4))

(square-list-map (list 1 2 3 4))

2.22


(define nil '())
(define (square x)
  (* x x))

(define (square-list-iter items)
  (define (iter things answer)
    (if (null? things)
        answer
        (iter (cdr things) 
              (cons (square (car things))
                    answer))))
   (iter items nil))

(define (square-list items)
  (define (iter things answer)
    (if (null? things)
        answer
        (iter (cdr things)
              (cons answer
                    (square (car things))))))
  (iter items nil))

(square-list-iter (list 1 2 3 4))
(square-list (list 1 2 3 4))

2.23


(define nil '())

(define (my-for-each proc items)
  (if (not (null? items))
      ((lambda() (proc (car items))
            (my-for-each proc (cdr items))))))

(my-for-each (lambda (x) (newline) (display x))
          (list 57 321 88))

2.24


(list 1 (list 2 (list 3 4)))

2.25


(define x1 (list 1 3 (list 5 7) 9))

(define x2 (list (list 7)))

(define x3 (list 1 (list 2 (list 3 (list 4 (list 5 (list 6 7)))))))

(car (cdr (car (cdr (cdr x1)))))

(car (car x2))

(car (cdr (car (cdr (car (cdr (car (cdr (car (cdr (car (cdr x3))))))))))))