(define (split-lines content)

  (let loop ((content content) (result '()) (line '()))

      ((? string? s) (string-split s #\newline))

      (() (append result (list line)))

      (((? string? s) content ...)

                   '()))))))))

(define (split-tr content)

  (let loop ((result '()) (lines (split-lines content)) (line-num 1))

    (match lines

      (() result)

(define (flatten-highlights highlights)

  (define (flatten-highlights-aux content tokens)

    (match content

      ((? string? s) (if (null? tokens)

                         `((,@tokens ,s))))

      (((? symbol? token) content ...)

       (flatten-highlights-aux content (cons token tokens)))

      ((? list? content)

       (append-map (lambda (c) (flatten-highlights-aux c tokens)) content))))

  (flatten-highlights-aux highlights '()))

(define (highlights->sxml highlights)

  (define (tag->class tag)

    (string-append "syntax-" (symbol->string tag)))

  (map (match-lambda

         ((? string? str) str)

         ((content ...)

  (if tag

      (lambda (tokens cursor)

        (let-values (((result remainder) (consume-until empty-tokens cursor)))

      consume-until))