Циклическая перестановка последнего элемента списка в начало

;; racket-lang.org
(define (last lst)
  (if (null? (cdr lst))
      (car lst)
      (last (cdr lst))))
 
(define (take-sub1 lst)
  (if (null? (cdr lst))
      null
      (cons (car lst) (take-sub1 (cdr lst)))))
 
(define (shr-cycle lst)
  (cons (last lst) (take-sub1 lst)))
 
(define (task n lst)
  (unless (and (integer? n) (>= n 0)) lst)
  (unless (list? lst) lst)
  (if (or (null? lst) (null? (cdr lst)))
      lst
      (let loop ((n n) (lst lst))
        (if (zero? n)
            lst
            (loop (sub1 n) (shr-cycle lst))))))
 
(task 3 '(1 2 3 4 5 6))
;'(4 5 6 1 2 3)

(defun cycle-swap (lst n)
 (if (zerop n) lst (cycle-swap (append (cdr lst) (list (car lst))) (- n 1))))
 
==> cycle-swap
 
(cycle-swap '(1 2 3 4 5) 2)
 
==> (3 4 5 1 2)

(defun cycle-swap (lst n)
 (if (zerop n) lst (cycle-swap (append (last lst) (butlast lst)) (- n 1))))
 
==> cycle-swap
 
(cycle-swap '(1 2 3 4 5) 2)
 
==> (4 5 1 2 3)

(defun f (lst n &aux (l (copy-list lst)) (len (length lst)))
            (setf (cdr (last l)) l)
            (subseq l n (+ n len)))

(defun rotate> (w n)
  (if (zerop n) w (rotate> (nconc (last w) (butlast w)) (1- n))))
 
> (rotate> '(1 2 3 4 5) 2)
(4 5 1 2 3)

(defun rotate> (w n)
  (if (zerop n) w (rotate> (cons (car (last w)) (butlast w)) (1- n))))
 
> (rotate> '(1 2 3 4 5) 2)
(4 5 1 2 3)

(defun rotate> (w n)
  (nconc  (last w n) (butlast w n)))
 
> (rotate> '(1 2 3 4 5) 2)
(4 5 1 2 3)

(defun butlast (ls)
  (if (cdr ls)
      (cons (car ls) (butlast (cdr ls)))))
 
(defun Cycle (ls n)
  (cond
    ((null ls) ())
    ((= 0 n) ls)
    (t (Cycle (cons (last ls) (butlast ls)) (- n 1)))))
 
Command: (Cycle '(1 2 3 4 5 6 7 8) 2)
(7 8 1 2 3 4 5 6)