SICP习题 1.17 (用加法求乘积)

(define (double x) (+ x x)) (define (halve x) (/ x 2)) (define (mult a b) (cond ((= b 0) 0) ((even? b) (double (mult a (halve b)))) ((odd? b) (+ a (mult a (- b 1)))))) (mult 12 12)

　　

(define (double x) (+ x x)) (define (halve x) (/ x 2)) (define (mult a b) (cond ((= b 0) 0) ((even? b) (mult (double a) (halve b))) ((odd? b) (+ a (mult a (- b 1)))))) (mult 12 12)

　　

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