(define split
  (lambda (str char skip count)
    (let ((len (string-length str)))
      (let loop ((index skip)
                 (last-index 0)
                 (result '()))
        (if (= index len)
            (reverse (cons (substring str last-index) result))
            (if (eq? char (string-ref str index))
                (loop (if (= count (+ 2 (length result)))
                          len
                          (+ index 1))
                      (+ index 1)
                      (cons char (cons (substring str last-index index)
                                       result)))
                (loop (+ index 1)
                      last-index
                      result)))))))

(define range-expand
  (lambda (str)
    (for-each
     (lambda (token)
       (if (char? token)
           (display token)
           (let ((range (split token #\- 1 2)))
             (if (null? (cdr range))
                 (display (car range))
                 (do ((count (string->number (list-ref range 0)) (+ 1 count))
                      (high (string->number (list-ref range 2))))
                     ((= count high) (display high))
                   (display count)
                   (display ","))))))
     (split str #\, 0 0))
    (newline)))