anchor.diff:  (in-package :coleslaw)
  +
  +(defvar *all-months* nil
  +  "The list of months in which content was authored.")
  +(defvar *all-tags* nil
  +  "The list of tags which content has been tagged with.")
   
   (defclass index ()
     ((slug :initarg :slug :reader index-slug)
  
positive.code: (defclass tag-index (index) ())
  
  (defmethod discover ((doc-type (eql (find-class 'tag-index))))
    (let ((content (by-date (find-all 'post))))
      (dolist (tag (all-tags))
        (add-document (index-by-tag tag content)))))
  
negative.code:    (content :initarg :content :reader index-content)))
  
  (defmethod render ((object index) &key prev next)
    (funcall (theme-fn 'index) (list :tags *all-tags*
                                     :months *all-months*
                                     :config *config*
                                     :index object
                                     :prev prev
  