在下面的代码中,我试图了解变量如何whatami
获取其值。在遵循逻辑时,我看到过程(lambda (y) (/ x y))
是我传递给方法的参数average-damp
,并且在该方法中表示为变量f
。似乎需要执行,但我无法弄清楚执行的顺序(/ x y)
。(average (f whatami) whatami)
任何帮助表示赞赏。
(define (average x y)
(/ (+ x y) 2))
(define (fixed-point f start)
(define tolerance 0.00001)
(define (close-enuf? u v)
(< (abs (- u v)) tolerance))
(define (iter old new)
(if (close-enuf? old new)
new
(iter new (f new))))
(iter start (f start)))
(define average-damp
(lambda (f)
(lambda (whatami) (average (f whatami) whatami))))
; square root with average damping
(define (_sqrt x)
(fixed-point
(average-damp (lambda (y) (/ x y)))
1))
(_sqrt 4.0)