Re: applying f to f n times - best argument order?

Kaz Kylheku wrote:

You want to bounce the arguments down into the recursive call, not a
list of them as one argument, right?
 
Is this what you are looking for:
 
 (defun ncall (f n &rest data)
   (loop repeat n
         for result = (apply f data) then (funcall f result)
         finally (return result)))

 
(define (feedback func init bottom-i :optional (top-i #f))
  (let ((result init))
    (if top-i
      (do ((i bottom-i (+ 1 i)))
        ((> i top-i)  result)
        (set! result (func result i)))
      (dotimes (i bottom-i)
        (set! result (func result))))
    result))


;; factorial
(feedback (lambda (prod i) (* i prod)) 1  1 5)
  ===>
120


(feedback (lambda (prod) (* 2 prod)) 1  8)
  ===>
256


;; Newton square root
(let ((x 99.0))
  (feedback
    (lambda (guess) (/. (+ guess (/. x guess)) 2.0))
    1.0  8))
  ===>
9.9498743710662

(sqrt 99)
  ===>
9.9498743710662