anchor.diff:  
   (defclass block-info ()
     ((common-size :type coordinate
  -                :initform (coerce 0 'coordinate)
  +                :initform (coordinate 0)
                   :accessor block-info-common-size)
      (number-of-cells :type integer
                       :initform 0
  
positive.code: 
  (defun block-info (block)
    "Returns information about the BLOCK in struct BLOCK-INFO."
    (let ((info (make-instance 'block-info)))
      (with-slots (common-size number-of-cells cell-sizes) info
                  (map-over-block-cells
  
negative.code:   (when (column-output-record-p record)
      (error "Trying to add a column into a row table.")))
  
  (defmethod table-cell-spacing ((table table-of-rows-output-record) stream)
    (parse-space stream (slot-value table 'x-spacing) :horizontal))
  (defmethod table-block-spacing ((table table-of-rows-output-record) stream)
    (parse-space stream (slot-value table 'y-spacing) :vertical))
  
  (defmethod table-equalize-column-widths ((table table-of-rows-output-record)
                                           block-infos widths)
    (declare (ignore table block-infos)
             (type (vector coordinate) widths))
    (let ((max-width
           (loop :for w :across widths
                 :maximize w)))
      (dotimes (i (length widths))
        (setf (aref widths i) max-width))))
  
  ;;; Table of columns
  (defclass table-of-columns-output-record (standard-table-output-record)
  