;; Add number attribute with appropriate value.

(=> (attribute "number"
	       (union (q-element 'title)
		      (q-element 'footnote)))
    (create-sub (origin (current-node))
		(subgrove-spec node: (current-node)
			       remove: '(implied?)
			       children: (number-attribute-children))
		property: 'attribute))

(define (number-attribute-children)
  (string->subgrove-spec-list
   (choose-element-number (origin (current-node)))))

;; Return string to be used as number of the element nd.

(define (choose-element-number nd)
  (cond ((match-element? nd 'footnote)
	 (number->string 
	  (list-ref (element-number-list '("chapter" "footnote") nd)
		    1)))
	((match-element? nd '(chapter title))
	 (number->string (ancestor-child-number "chapter" nd)))
	((match-element? nd '(section title))
	 (format-number-list
	  (hierarchical-number '("chapter" "section") nd)
	  "1"
	  "."))))

(define (string->subgrove-spec-list s)
  (map (lambda (ch)
	 (subgrove-spec class: 'data-char add: `((char ,ch))))
       (string->list s)))