sicp 习题2.24 && 2.25

它的盒子图形如下：

 (1 (2 (3 4)))       ((2 (3 4)))[*]---------------> [*] |                   | |                   | v                   v (2 (3 4))         ((3 4)) 1                  [*]---------------> [*]                     |                   |                     |                   |                     v                   v (3 4)             (4)                     2                  [*]---------------> [*]---------------> '()                                         |                   |                                         |                   |                                         v                   v                                         3                   4它的树图形如下： (1 (2 (3 4)))   *  / \ /   \  (2 (3 4))1     *     / \    /   \  (3 4)   2     *        / \       /   \      3     4

习题2.5

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

run:

Welcome to DrRacket, version 5.3.3 [3m].
Language: planet neil/sicp; memory limit: 512 MB.
> (car (cdr (car (cdr (cdr x))))) 
7
> 

#lang planet neil/sicp(define x (list (list 7)))

run:

> (car x)
(mcons 7 '())
> (caar x)
7
> 

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

run:

> (car (cdr (car (cdr (car (cdr (car  (cdr (car (cdr (car (cdr x))))))))))))
7
>