anchor.diff:       (setf circle-check? 'not-first-p))
     `(let ((*current-level* (1+ *current-level*))
            (*current-length* -1)
  -         (*parents* *parents*)
            ,@(if (and circle-check? atsign?) `((not-first-p (plusp *current-length*)))))
        (unless (check-block-abbreviation ,var ,args ,circle-check?)
          (block logical-block
  
positive.code:   nil)
  
  (defmethod mezzano.gray:stream-clear-output ((stream xp-structure))
    (let ((*locating-circularities* 0)) ;hack to prevent visible output
      (attempt-to-output stream T T)
      (clear-output (base-stream stream)))
    nil)
  
  ;note we are assuming that if a structure is defined using xp::defstruct,
  
negative.code:       (setf *abbreviation-happened* '*print-lines*)
        (throw 'line-limit-abbreviation-exit T))
      (incf (line-no xp))
      (unless (locating-circularities xp)
        (write-line
            (buffer xp) (base-stream xp) :end end))))
  
  