我去

参考这里;3.16(define (count-pairs x) (if (not (pair? x)) 0 (+ (count-pairs (car x)) (count-pairs (cdr x)) 1)));;4个(define x '(a b))(define y (cons (cdr x) x))(count-pai

;leaf(define (make-leaf symbol weight) (list 'leaf symbol weight))(define (symbol-leaf leaf) (cadr leaf))(define (weight-leaf leaf) (caddr leaf))(define (leaf? obj) (eq? 'leaf (car obj)));

(define (append a b) (if (null? a) b (cons (car a) (append (cdr a) (cons (car a) b)))))(define nil (list))(define (count-leaves x) (cond ((null? x) 0) ((not (pair? x)) 1)

;balance在全局环境里，没什么好说的(define balance 100)(define (withdraw amount) (if (>= balance amount) (begin (set! balance (- balance amount)) balance) "insufficent funds"));求值new-wi

(define (interleave s1 s2) (if (empty-stream? s1) s2 (cons-stream (stream-car s1) (interleave s2 (stream-cdr s1)))))(define (pairs s t) (cons-stream (list (stream-ca

;流实现的行为方式;delay和force的实现(define (memo-proc proc) (let ((already-run? false) (result false)) (lambda () (if already-run? result (begin (set! already-run? tr

;系统地将迭代操作方式表示为流过程(define (sqrt-stream x) (define guesses (cons-stream 1.0 (stream-map (lambda (guess) (/ (+ guess (/ x guess)) 2)) guesses)))

表达式的表示

;书上的let并不是必须的(define (integral delayed-integrand initial-value dt) (define int (cons-stream initial-value (add-streams (scale-stream (force delaye

;4.12，这里的用了一个通用的在框架中寻找变量的过程，不过这个过程不能用在4.13中的make-unbound!里(define (lookup-var-in-frame var vars vals) (cond ((null? vars) false) ((eq? var (car vars)) (cons vars vals)) (else (lookup

(define (element-of-set? x set) (cond ((or (null? set) (> (car set) x)) #f) ((= x (car set)) #t) (else (element-of-set? x (cdr set)))))(define (intersaction-set set1 set2) (cond ((

;连接器的表示;user不需要也不能添加进constraints表里面,并且只有实现connect过的constraint才能进行set-value!(define (make-connector) (let ((value false) (informant false) (constraints '())) (define (set-my-value! new-value set

(define (make-queue) (cons '() '()))(define (front-ptr queue) (car queue))(define (rear-ptr queue) (cdr queue))(define (empty-queue? queue) (null? (front-ptr queue)))(define (set-front-ptr!

看完这一节，感觉世界观又被重塑。 首先说说这一小节的标题”序列作为一种约定的界面”是什么意思:这句话意思是序列作为程序不同模块间数据流动的形式。 学习lisp语言不久，lisp就给了我很多惊喜，我特地新建了一个文件夹叫astonishing来放代码☺ 下面是这一节我的代码：(define nil (list));(define (enumerate-tree-leaves t) (co

正如书中写的一样(“还不足以令人如雷灌顶是吧？！！”)，看到完全没有数实现加一和0的定义，着实吓了一跳。 当然了，既然你不走寻常路，那我也不能在一棵树上吊死，你说不用数字，那至少得体现数的概念吧？多少个苹果是数，函数迭代多少次也是数（哈哈，其实是从书上的代码看出点端倪，然后顺藤摸瓜推出来的）。 嗯哼，揭晓答案：这里的数n对应的是f迭代n次，如果n是0，n对应的就是自变量。(define zero

这又是一个让我感到很惊讶的thing,让我们理清一下思路： 现在我们是要实现cons,car以及cdr,使得(car (cons x y))=x,(cdr (cons x y))=y,cons由我们自己定义,它的值要么是数，要么是函数，一般情况下，用数将两个量结合还能区分开来是比较困难的，那么cons应该返回一个函数，这个函数要能根据接受的参数返回x或y,这个参数可以是同一个函数的不同参数，也可以

本小节代码需要和”序列操作”那节的代码在一起运行;嵌套映射(define (make-pairs1 n) (define (i-iter i ans) (define (j-iter j ansi) (if (= j 0) ansi (j-iter (- j 1) (cons (list i j) ansi)))) (if (

;一维表格(define (make-table) (list '*table*))(define (assoc key records) (cond ((null? records) #f) ((equal? (caar records) key) (car records)) (else (assoc key (cdr records)))))(de

mit-scheme里没有直接提供wave和rogers这两个过程，但是DrRacket提供einstein，只需加上开头两行就可使用#lang racket(require (planet "sicp.ss"("soegaard""sicp.plt" 2 1)))(define wave einstein)(define wave2 (beside wave (flip-vert wav

这一章通过实现图形语言的过程体现了程序的层次性(define device (make-graphics-device (car (enumerate-graphics-types))))(define (draw-line start end) (graphics-draw-line device (xcor-vect start) (y

;基本功能块;延时:(define inverter-delay 2)(define and-gate-delay 3)(define or-gate-delay 5);inverter(define (inverter input output) (define (invert-input) (let ((new-value (logical-not (get-signal

(define random-init 1)(define (rand-update x) (remainder (+ (* 13 x) 5) 24))(define (random-numbers op-stream) (define (numbers last-value op-stream) (let ((op (stream-car op-stream)))