46-fixed-point.scm

(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))