anchor.diff:    (destructuring-bind (section (formattedcode (pre text))) expr
       (declare (ignore section formattedcode pre))
       `(:pre ,@(nth-value 1 (markup-lite (cons text 0))))))
  +
  +(defun embedded-tweet (tree)
  +  (let ((text (tag-text :text tree))
  +        (screenname (tag-text :screenname tree))
  +        (handle (tag-text :handle tree))
  +        (id (tag-text :id tree))
  +        (date (tag-text :date tree)))
  +    `(:progn
  +       ((:blockquote :class "twitter-tweet" :lang "en")
  +        (:p "“" ,text "”")
  +        (:noescape "&mdash;")
  +        ,screenname "(@" ,handle ") "
  +        ((:a :href (:format "https://twitter.com/~a/status/~a" ,handle ,id)) ,date))
  +       (:script :async "async" :src "https://platform.twitter.com/widgets.js" :charset "utf-8"))))
  +
  +(defun tweet-by-id (tree)
  +  (let ((filename (make-pathname :defaults (merge-pathnames "tweets/") :name (just-text tree))))
  +    `(:noescape ,(file-text filename))))
  +
  +(defun chart (tree)
  +  `(:div :class "chart" :id (:format "chart~a" ,(just-text tree))))
  +
  +(defun tag-text (tag tree)
  +  (mapcan #'just-text (extract tag tree)))
  +
  +(defun include-from-file (tree)
  +  (let* ((text (string-trim " " (just-text tree)))
  +         (spc (position #\Space text))
  +         (file (subseq text 0 spc))
  +         (name (subseq text (1+ spc)))
  +         (contents (file-text file))
  +         (lines (split-sequence #\Newline contents)))
  +    (flet ((start (line) (search (format nil "8<--- ~a" name) line))
  +           (end (line) (search "8<----" line)))
  +      (let* ((start (cdr (member-if #'start lines)))
  +             (end (member-if #'end start)))
  +        (if end
  +            `(:pre ,(format nil "~{~&~a~}" (ldiff start end)))
  +            (error "Coludn't find include section ~a in ~a" name file))))))
  
positive.code:                   `((:style (:noescape ,style)))
                    `((:link :href ,style :rel "stylesheet"))))))
  
  (defun enscript (script)
    "Add an SCRIPT tag if script is provided."
    (if script
        (rewriter :body (appending `((:script :src ,script :type "text/javascript"))))
        #'identity))
  
  ;;; Helper functions ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
  
  
negative.code:                  (cons (mapcar #'walk x)))))
        (walk sexp))))
  
  (defun formatted-code-section (expr)
    (and
     (consp expr)
  