anchor.diff:  (defun emit (bytes) (context-emit *context* bytes))
   
   (defun label (name &optional (offset 0))
  +  (assert (not (null *context*)))
     (let ((context *context*))
  -    (unless context (error "Label ~A referenced in null context!" name))
  -    (delay ()
  +    (delay name (offset)
         (+ offset
            (or (context-find-label context name)
                (error 'resolvable-condition
  -                    :text (format nil "Label ~A is undefined" name)))))))
  +                    :path (format nil "Label ~A is undefined" name)))))))
   
   (defun set-label (name)
     (context-set-label *context* name)
  
positive.code: 
  (defmethod parameter-bytes ((mode indirect))
    (encode-word
     (delay ((address (parameter mode)))
       (if (= #xFF (logand address #xFF))
           (error "Indirect jump through ~X tickles 6502 page wraparound bug." address)
           address))))
  
negative.code: (defun rel (label)
    (let ((addr (context-address *context*))
          (label (label label)))
      (relative (delay :relative (label) (- label addr 2)))))
  
  ;;; Instruction parameters, according to addressing mode
  
  