Re: Finding Average without using Recusrion only using Prog

On 6/16/2024 11:28 AM, HenHanna wrote:

On 6/15/2024 9:39 PM, B. Pym wrote:

     (defun avg (args)
       (loop for x in args
           for l upfrom 1
           summing x into tot
           finally (return (/ tot l))))

>
Gauche Scheme
>
(use gauche.collection) ;; fold2
>
(define (add&count n sum cnt) (values (+ sum n) (+ cnt 1)))
>
(define (avg nums)
   (apply /
     (values->list
       (fold2
         add&count
         0 0
         nums))))
>
(avg '(20 30 40 50 60 70 80))     ===>   50

  Nice...    Here's a more boring version:
  (define (ave x)
   (let ((L (length x)))
     (if (> L 0)
       (/ (fold + 0 x) L))))
 (define (Pave x)   (format #t "~%    ~S  ~S  ~%" x (ave x)))
 (Pave  '(1 2 3))
(Pave  '(1 2 3 4))
(Pave  '(1))
(Pave  '())
 

(define-macro (ave x)
   `(/ (+ ,@ (map (lambda (n) `(+ ,@ (make-list n 1))) (cadr x)))
       (+ ,@ (map (lambda (n) 1) (cadr x)))))
(print (ave  '(1)))
(print (ave  '(1 2 3)))
gosh> (macroexpand '(ave '(1 2 3)))
          ==>        (/ (+ (+ 1) (+ 1 1) (+ 1 1 1)) (+ 1 1 1))