anchor.diff:  
   (defun (setf macro-function) (new-function symbol &optional environment)
     (unless (null environment)
  -    (error 'type-error :datum environment :expected-type null))
  +    (error 'type-error :datum environment :expected-type 'null))
     (unless (symbolp symbol)
       (error 'type-error :datum symbol :expected-type 'symbol))
     (unless (functionp new-function)
  
positive.code:     ;; FIXME: handle more proclamations
      ))
  
  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
  ;;;
  ;;; Put some stuff in the global environment.
  
  (add-to-global-environment
   (make-constant-variable-entry 'pi pi))
  
  (add-to-global-environment
   (make-special-variable-entry '*read-base*))
  
  (add-to-global-environment
   (make-global-function-entry 'car))
  
  (add-to-global-environment
   (make-global-function-entry 'error))
  
  (add-to-global-environment
   (make-global-function-entry '(setf fdefinition)))
  
  (add-to-global-environment
   (make-global-function-entry 'funcall))
  
  (add-to-global-environment
   (make-local-macro-entry
    'when
    (lambda (form env)
      (declare (ignore env))
      `(if ,(cadr form)
  	 (progn ,(cddr form))
  	 nil))))
  
  
negative.code:     (error 'type-error :datum symbol :expected-type 'symbol))
    (let ((entry (find-if (lambda (entry)
  			  (and (typep entry 'special-operator-entry)
  			       (eq (name entry) symbol)))
  			(functions *global-environment*))))
      (not (null entry))))
  
  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
  