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

On 8/25/2024 4:04 AM, B. Pym wrote:

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))

Isn't this where you usually jump in and loudly proclaim "SHORTER!"? You might as well repeat it hear since you are not shorter a significant amount of the time.
Off topic question: Any job offers recently?

;; 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

--
Jeff Barnett