Перестроить список в список средних арифметических элементов циклом

(defun task (lst (s (apply '+ lst))) 
  (loop while (not ((null lst) nil)) do(
  (t (cons (/ (- s (car lst)) l) )))))

(defun task (lst &aux (s (apply '+ lst)) (l (- (length lst) 1)))
  (let ((r nil))
    (dolist (i lst (reverse r))
      (push (/ (- s i) l) r))))
 
==> task
 
(task '(1 2 3 4 5 6 7))
 
==> (9/2 13/3 25/6 4 23/6 11/3 7/2)

(defun aver-sine (w
                  &optional
                  (s (reduce #'+ w))
                  (n (1- (length w))))
  (loop for a in w collect (/ (- s a) n)))
 
> (aver-sine '(1 2 3 4 5))
(7/2 13/4 3 11/4 5/2)
> (aver-sine '(1 2 3 4 5 6 7))
(9/2 13/3 25/6 4 23/6 11/3 7/2)

(defun aver-sine (w
                  &optional
                  (s (reduce #'+ w))
                  (n (1- (length w))))
  (when (cdr w) (loop for a in w collect (/ (- s a) n))))
 
> (aver-sine '(1 2 3 4 5 6 7))
(9/2 13/3 25/6 4 23/6 11/3 7/2)
> (aver-sine '(1))
NIL
> (aver-sine '(1 2))
(2 1)
> (aver-sine '(1 2 2))
(2 3/2 3/2)

#lang scheme
 
(define (do-work l)
  (for/list ([i l])
    (/ (- (apply + l) i) (- (length l) 1.0))))
 
(do-work '(1 2 3 4 5))