CLOS class instances are implemented with handles for a very important reason: so slots can be added to classes dynamically, even if live instances exist. In d

CLOS class instances are implemented with handles for a very important reason: so slots can be added to classes dynamically, even if live instances exist. In decades of Common Lisp programming I think I've written a CHANGE-CLASS call maybe twice, but I add slots to classes all the time (and occasionally remove them).