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;;;; Under Creative Commons Attribution-ShareAlike 4.0
;;;; International. See
;;;; <https://creativecommons.org/licenses/by-sa/4.0/>.
;;;;
(define-module (net ricketyspace sicp one fortysix)
#:export (fixed-point fp-sqrt))
(define (iterative-improve good-enough? improve)
(define (try guess)
(let ((next (improve guess)))
(if (good-enough? guess next)
next
(try next))))
try)
(define (fixed-point f guess)
(define tolerance 0.00001)
(define (close-enough? v1 v2)
(< (abs (- v1 v2)) tolerance))
((iterative-improve close-enough? f) guess))
(define (fp-sqrt x)
(define (average x y) (/ (+ x y) 2.0))
(fixed-point (lambda (y) (average y (/ x y)))
1.0))
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