anchor.diff:              [(string/find (string/char-at str 1) "#")
                (let* [((start end match)
                        (string/find str "#([a-zA-Z][^:%%@]*)"))]
  -               (values-list (list 'implicitly-named match) end))]))]
  +               (values-list (list 'implicitly-named match) end))]
  +            [else
  +              (let* [(pos (.> last-pos-ref 1))]
  +                (.<! last-pos-ref 1 (+ pos 1))
  +                (values-list (list 'positional pos) 1))]))]
       (values-list val (string/sub str (+ 1 end)))))
   
   (defun display-with-sep (sep frag) :hidden
  
positive.code:             (k (parse-format-formatter fmtr))]
         (lambda (ref)
           (list 'urn-format ref (display-with-sep (string/sub sep 2 (- (n sep) 1)) (k 'ignored)))))]
      [(= spec "") (lambda (ref) (list 'urn-format ref `pretty))]))
  
  (defun handle-formatting-specifier (spec last-pos) :hidden
    "Parse the entirety of the format specifier SPEC."
    (let* [((ref spec) (parse-format-reference spec))
           ((formatter spec) (parse-format-formatter spec))]
    (values-list (formatter ref) last-pos)))
  
  (defun parse-format (str) :hidden
    "Parse the format string STR into a list of fragments."
    (let* [(cur "") ; the current character (for convenience)
           (buf "") ; a buffer
           (last-positional 1) ; for anonymous positions
           (frags '())]
      (loop [(i 1)]
        [(> i (n str))
  
negative.code:            [(or (>= j (n str))
                  (= (string/char-at str j) "}"))
              (set! i j)
              (let* [(frag (handle-formatting-specifier parsed last-positional))]
                (push-cdr! frags frag))]
             (recur (.. parsed (string/char-at str j)) (+ 1 j)))]
          [else => (set! buf (.. buf it))])
  