anchor.diff:    (loop for s in (closer-mop:class-slots (class-of instance))
        for slot-name = (slot-definition-name s)
        when (slot-boundp instance slot-name)
  -     collect (cons (intern (symbol-name slot-name) :keyword) 
  +     collect (cons (intern (symbol-name slot-name) :keyword)
   		   (slot-value instance slot-name))))
   
   (defun alist (&rest k/v-pairs)
  
positive.code: 		   res (if (eq eof exp)
  			   :eof
  			   (mapcar
  			    (lambda (v) (alist :type (type-tag v) :value (write-to-string v))) 
  			    (multiple-value-list (eval exp))))))
  	      (error (e) 
  		(setf res (list
  			   (alist 
  			    :type 'error 
  			    :value (front-end-error (format nil "~s" exp) e)))))))))
      (if (eq :eof res)
  	nil
  
negative.code: 
  (defun stringified-error-prop? (prop-name)
    (member prop-name
  	  '(:name :new-function :specializers :old-method :datum :expected-type :generic-function)))
  
  (defun front-end-error (form e)
    "Takes a form and an error pertaining to it.
  