;;;; Aplicand recursia si variabile colectoare din lista de atomi arbitrari L
;;;; sa se elimine toti atomii numerici
(DEFUN remove-numbers (L &OPTIONAL REZ)
    (COND
        ((NULL L) REZ)

        ((NUMBERP (CAR L))
            (remove-numbers (CDR L) REZ)
        )

        (T (REVERSE
            (remove-numbers
                (CDR L)
                (CONS (CAR L) REZ)
            )
        ))
    )
)

(SETQ L `(A 4 C 1 D 3))
(WRITE (remove-numbers L)) ; (A C D)