anchor.diff:    value)
   
   #+ccl (deftype weak-list () 'ccl:population)
  -#+ccl (defun make-weak-list (list) (ccl:make-population :initial-contents list))
  +#+ccl (defun make-weak-list (list) (check-type list list) (ccl:make-population :initial-contents list))
   #+ccl (defun weak-list-p (wl) (and (typep wl 'ccl:population) (eq :list (ccl:population-type wl))))
   #+ccl (defun weak-list-list (wl) (ccl:population-contents wl))
   #+ccl (defun (setf weak-list-list) (value wl) (setf (ccl:population-contents wl) value))
  
positive.code:                 (gethash '%weak-object% h) object)
            h))
  
  #-(and clisp debug-weak)
  (defun weak-pointer-p (object)
    "Returns true if the object is of type WEAK-POINTER."
    #+allegro                (typep object 'weak-pointer)
  
negative.code: #-(and (or ccl clisp))
  (defun make-weak-list (list)
    "Creates a WEAK-LIST pointing to each of the elements in the given list."
    (check-type list list)
    (%make-weak-list :head (mapcar (function make-weak-pointer) list)))
  
  #-(and (or ccl clisp) (not debug-weak))
  (defun weak-list-list (weak-list)
  