defined, and any @var{init-value} argument is unused. @var{place}
can be a different named variable (which you must define yourself), or
anything that can be used with the @code{setf} function
-(@pxref{Generalized Variables,,, cl, Common Lisp Extensions}).
+(@pxref{Generalized Variables}).
@var{place} can also be a cons @code{(@var{get} . @var{set})},
where @var{get} is an expression that returns the current state,
and @var{set} is a function of one argument (a state) that sets it.