文責: | @naoiwata |
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(define (new-if predicate then-clause else-clause)
(cond (predicate then-clause)
(else else-clause)))
(new-if (= 2 3) 0 5)
(new-if (= 1 1) 0 5)
(define (sqrt-iter guess x)
(new-if (good-enough? guess x)
guess
(sqrt-iter (improve guess x)
x)))
(define (improve guess x)
(average guess (/ x guess)))
(define (average x y)
(/ (+ x y) 2))
(define (good-enough? guess x)
(< (abs (- (square guess) x)) 0.001))
(define (square x) (* x x))
(define (sqrt x)
(sqrt-iter 1.0 x))
(sqrt 3)