# OBJECT introduce simple mutable structures
[hear] (define mutable-struct /
? lst /
let ((data (map (? x / make-cell 0) (lst))))
(? key /
list-ref (data) (list-find (lst) (key) (? x 0))));
[hear] (define test-struct1 /
mutable-struct /
vector item1 item2 item3);
[hear] (set! (test-struct1 item1) 15);
[hear] (= (get! / test-struct1 item1) 15);