CL-USER> (gethash :foo #{:foo :bar :baz :quux}#)
:BAR
T
CL-USER> (let ((m #{:foo :bar :baz :quux}#))
(sethash :baz :woz m)
(hashkeys m))
(:BAZ :FOO)
CL-USER> (hashtable-to-alist #{:a :b :c :d}#)
((:C . :D) (:A . :B))