标签：style strong ar line python mil a height
解：
公共过程
(define (even? n) (= (remainder n 2) 0)) (define (double n) (+ n n)) (define (halve n) (/ n 2))
1.16：
(define (expt b n) (define (iter b n a) (cond ((= n 0) a) ((even? n) (iter (* b b) (/ n 2) a)) (else (iter b (- n 1) (* b a))))) (iter b n 1))
1.17 1.18：
= 2*(a*(b/2))=a*(b/2)+a*(b/2)=2a*(b/2),b是偶数
a*b = a+a*(b-1)，b是奇数
= a，b=1
(define (multiply a b) (define (fast-mul a b) (cond ((= b 1) a) ((even? b) (double (fast-mul a (halve b)))) (else (+ a (fast-mul a (- b 1)))))) (fast-mul a b)) (define (multiply2 a b) (define (fast-mul a b c) (cond ((= b 1) (+ a c)) ((even? b) (fast-mul (double a) (halve b) c)) (else (fast-mul a (- b 1) (+ a c))))) (fast-mul a b 0))
SICP 1.16 1.17 1.18,布布扣,bubuko.com
标签：style strong ar line python mil a height
原文地址：http://my.oschina.net/u/1445655/blog/295062
