SICP 练习1.35使用不动点发寻找黄金分割律

前几个输出是书上介绍不动点法的几个样例

(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))

(newline)
(display (fixed-point cos 1.0))

(newline)
(display (fixed-point (lambda (y) (+ (sin y) (cos y))) 1.0))

(define (sqrt x)
  (fixed-point (lambda (y) (average y (/ x y))) 1.0))

(define (average x y)
  (/ (+ x y) 2))

(newline)
(display (sqrt 2))

(newline)
(display (fixed-point (lambda (x) (+ 1 (/ 1 x))) 1.0))