;gnu clisp 2.49

(defun prvek (L X)
    (cond ( (null L) () )
          ( (atom (car L))(or (= (car L) X) (prvek (cdr L) X)) )
          ( t (or (prvek (cdr L) X) (prvek (car L) X)) )
    )
)

;(print (prvek '(1 2 (3)) 3))

(defun pocet (L)
    (cond ( (null L) 0 )
          ( t  (+ 1 (pocet (cdr L))) )
    )
)

;(print (pocet '(1 2 3 4)))

(defun pocet2 (L)
    (cond ( (null L) 0 )
          ( (atom (car L)) (+ 1 (pocet2 (cdr L))) )
          ( t (+ (pocet (car L)) (pocet(cdr L))) )
    )
)

;(print (pocet2 '(1 2 (3 4) 5 6)))

(defun pocet3(L)
  (cond
    ((null L) 0)
    ((atom L) 1)
    (t (+ (pocet3 (car L)) (pocet3 (cdr L))))))

;(print (pocet3 '(1 2 (3 4) 5 () 6)))