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;;; Under Creative Commons Attribution-ShareAlike 4.0
;;; International. See
;;; <https://creativecommons.org/licenses/by-sa/4.0/>.
(define-module (one six)
#:export (sqrt-sicp sqrt-nif square good-enough? new-if improve))
(define (square x)
(* x x))
(define (good-enough? guess x)
(< (abs (- (square guess) x)) 0.001))
(define (average x y)
(/ (+ x y) 2))
(define (improve guess x)
(average guess (/ x guess)))
(define (new-if predicate then-clause else-clause)
(cond (predicate then-clause)
(else else-clause)))
(define (sqrt-iter guess x)
(if (good-enough? guess x)
guess
(sqrt-iter (improve guess x)
x)))
(define (sqrt-iter-nif guess x)
(new-if (good-enough? guess x)
guess
(sqrt-iter-nif (improve guess x)
x)))
(define (sqrt-sicp x)
(sqrt-iter 1.0 x))
(define (sqrt-nif x)
(sqrt-iter-nif 1.0 x))
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