Функция объединения двух списков

(defun -union (w v)
  (cond ((null w)  v)
    ((member (car w) v) (-union (cdr w) v))
    ((cons (car w) (-union (cdr w) v)))))
 
> (-union '(1 2 3) '(2 3 4))
(1 2 3 4)

(defun union* (set1 set2)
  (append set1 (remove-if #'(lambda (x) (member x set1)) set2)))
 
==> union*
 
(union* '(1 2 3) '(2 3 4))
 
==> (1 2 3 4)
 
 
(defun union$ (set1 set2) ;; HomeLisp
  (let ((res set1))
    (iter (for x in set2) (unless (member x set1) (collecting x into res)))
    res))
 
==> union$
 
(union$ '(1 2 3) '(2 3 4))
 
==> (1 2 3 4)
 
(defun union& (set1 set2) ;; HomeLisp
  (setof (append set1 set2)))
 
==> union&
 
(union& '(1 2 3) '(2 3 4))
 
==> (1 2 3 4)

; racket-lang.org
 
(define (foo . lst)
  (remove-duplicates (flatten lst)))
 
(foo '(1 2 3) '(2 3 4 5) '(3 4 5 6))
;'(1 2 3 4 5 6)