If you have followed this example from the beginning, the interface and its callbacks are now completely specified. Next, you can create a Common Lisp system which integrates the interface definition with the callback code.
:members ("ib-callbacks" "ib-example"))
This form creates a system called
that contains two members;
(the file containing the interface definition) and
(the file containing the callback code).
ib-callbacks.lispfiles, and call this file