Accessor Modifier oldf place

oldf simply modifies the behavior of the storing form of place so that it returns the old values of the place instead of the new ones.

(let ((a 5))
  (values (incf (oldf a) 2)
          a))
⇒ 5, 7
(let ((a 5))
  (values (setf (oldf a) 10)
          a))
⇒ 5, 10
(let ((list '(1 2 3)))
  (values (push 0 (oldf list))
          list))
⇒ (1 2 3), (0 1 2 3)