Hypothetical implementation of CONS:
(DEFINE-PREDICATE PAIR?)
(DEFINE-SETTABLE-OPERATION (CAR PAIR))
(DEFINE-SETTABLE-OPERATION (CDR PAIR))(DEFINE (CONS THE-CAR THE-CDR)
(OBJECT NIL
((PAIR? SELF) T)
((CAR SELF) THE-CAR)
((CDR SELF) THE-CDR)
(((SETTER CAR) SELF NEW-CAR) (SET THE-CAR NEW-CAR))
(((SETTER CDR) SELF NEW-CDR) (SET THE-CDR NEW-CDR))))