(let ((table (make-hash-table)))
  (list-ec (: i 0 2) (: j 0 2)
           (hash-table-update!/default table (list i j)
                                       (lambda (x)
                                         (append x (list j)))
                                       (list j))
           (hash-table->alist table)))
;;; Result:   (((0 1) 1 1) ((1 0) 0 0) ((1 1) 1 1) ((0 0) 0 0))
;;; Expected: (((0 1) 1)   ((1 0) 0)   ((0 0) 0)   ((1 1) 1))