(use srfi-69)

(define objtbl (make-hash-table eq?))

(define (register! obj arg)
  (hash-table-update! objtbl obj identity (lambda () (list obj arg))))

(assert (eq? (register! 1 1) (register! 1 2)))

(define-record foo bar)

(define o1 (make-foo (list 23)))

(define r1 (register! o1 1))

(assert (eq? r1 (register! o1 2)))
(assert (eq? r1 (register! o1 3)))
(foo-bar-set! o1 (list 42))
#;(assert (eq? r1 (register! o1 4)))
(unless
 (hash-table? (hash-table-ref/default objtbl o1 #f))
 (assert
  (not (hash-table-fold objtbl
			(lambda (k v i) (or i (eq? k o1)))
			#f))))