+;;; FIXME: Why are there two layers here, with one operator trivially
+;;; defined in terms of the other? It'd be nice either to have a
+;;; comment explaining why the separation is valuable, or to collapse
+;;; it into a single layer.
+;;;
+;;; FIXME (?): These are logically inline functions, but they need to
+;;; be SETFable, and for now it seems not worth the trouble to DEFUN
+;;; both inline FOO and inline (SETF FOO) for each one instead of a
+;;; single macro. Perhaps the best thing would be to make them
+;;; immutable (since it seems sort of surprising and gross to be able
+;;; to modify hash values) so that they can become inline functions
+;;; with no muss or fuss. I (WHN) didn't do this only because I didn't
+;;; know whether any code anywhere depends on the values being
+;;; modified.