anchor.diff:  ;;; of that entry does not contain +unbound+.
   
   (defun boundp (symbol)
  -  (unless (symbolp symbol)
  -    (error 'type-error :datum symbol :expected-type 'symbol))
  +  (declare (cl:type symbol symbol))
     (not (null (or (find symbol (constant-variables *global-environment*)
   		       :key #'name :test #'eq)
   		 (find symbol (symbol-macros *global-environment*)
  
positive.code: ;;; to call FDEFINITION to do the work. 
  
  (defun symbol-function (symbol)
    (unless (symbolp symbol)
      (error 'type-error :expected-type 'symbol :datum symbol))
    (fdefinition symbol))
  
  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
  
negative.code: ;;; attempt is made to make a constant variable unbound.
  
  (defun makunbound (symbol)
    (declare (cl:type symbol symbol))
    ;; Check whether the symbol has a definition as a constant variable.
    (let ((constant-variable-entry
  	  (find symbol (constant-variables *global-environment*)
  