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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 thirtyfive)
#:export (golden-ratio))
(define tolerance 0.00001)
(define (fixed-point f first-guess)
(define (close-enough? v1 v2)
(< (abs (- v1 v2)) tolerance))
(define (try guess)
(let ((next (f guess)))
(if (close-enough? guess next)
next
(try next))))
(try first-guess))
(define (golden-ratio )
(fixed-point (lambda (x) (+ 1 (/ 1.0 x))) 1.0))
;;; Guile REPL
;;;
;;; scheme@(guile-user)> ,use (net ricketyspace sicp one thirtyfive)
;;; scheme@(guile-user)> (golden-ratio)
;;; $1 = 1.6180327868852458
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