Re: Finding Average without using Recusrion only using Prog

On 2024-06-16, HenHanna <HenHanna@devnull.tb> 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  '())

This is the TXR Lisp interactive listener of TXR 294.
Quit with :quit or Ctrl-D on an empty line. Ctrl-X ? for cheatsheet.
Evidence of amphoric Lisp macros was recently found in ancient clay
jars.
1> [[callf / sum len] '(1 2 3 4)]
2.5

callf: return a function which:

- applies the second and subsequent functions given to callf (here sum
  and len) to its arguments.
- applies the first argument of callf (here /) to the resulting
  values.
- returns the resulting value

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