(define (divider? ch)
  (or (equal? ch #\tab)
      (equal? ch #\newline)
      (equal? ch #\space)))

(define (empty? str)
  (define (rec str len i)
    (or (= i len)
        (and (divider? (string-ref str i))
             (rec str len (+ i 1)))))
  (rec str (string-length str) 0))

(define (read-words)
  (define (rec xs str)
    (let ((ch (read-char)))
      (if (eof-object? ch)
          (if (empty? str)
              xs
              (append xs (list str)))
          (if (divider? ch)
              (if (empty? str)
                  (rec xs "")
                  (rec (append xs (list str)) ""))
              (rec xs (string-append str (string ch)))))))
  (rec '() ""))