10Jun/090
Exercise 1.18 of SICP
Exercise 1.18: Using the results of exercises 1.16 and 1.17, devise a procedure that generates an iterative process for multiplying two integers in terms of adding, doubling, and halving and uses a logarithmic number of steps.
(define (double x) (+ x x)) (define (halve x) (/ x 2)) (define (fast-mult-iter a b n) (cond ((= b 0) n) ((even? b) (fast-mult-iter (double a) (halve b) n)) (else (fast-mult-iter a (- b 1) (+ a n)))))