anchor.diff:  ;;; method for optimization purposes.
   (defun add-writer-method (class function-name slot-definition)
     (let* ((lambda-list '(new-value object))
  +	 ;; See comment above as to why we do not call
  +	 ;; ENSURE-GENERIC-FUNCTION directly here.
   	 (generic-function (ensure-accessor-function function-name lambda-list))
   	 (specializers (list *t* class))
   	 (method-function
  
positive.code: 
  ;;;; This file contains very basic versions of the functions
  ;;;; ADD-READER-METHOD and ADD-WRITER-METHOD.  These functions are not
  ;;;; part of the spcification, but they conventient abstractions that
  ;;;; are called when a class metaobject is created that has one or
  ;;;; more slots with a :READER, :WRITER, or :ACCESSOR slot option.
  ;;;; Specifically, they are called from the :AFTER methods on
  ;;;; INITIALIZE-INSTANCE specialized for STANDARD-CLASS and
  ;;;; FUNCALLABLE-STANDARD-CLASS.
  
  ;;; Add a reader method to a generic function.  CLASS is a class
  ;;; metaobject that plays the role of specialize for the argument of
  
negative.code: ;;; method for optimization purposes. 
  (defun add-reader-method (class function-name slot-definition)
    (let* ((lambda-list '(object))
  	 ;; See comment above as to why we do not call
  	 ;; ENSURE-GENERIC-FUNCTION directly here.
  	 (generic-function (ensure-accessor-function function-name lambda-list))
  	 (specializers (list class))
  	 (method-function
  