format (№1 19)

(define (format namein nameout . str)
  (define in (open-input-file namein))
  (define out (open-output-file nameout #:exists 'replace))
  (define (iter)
    (define n (read-line in  ))
    (if (equal? n eof) (close-output-port out) (help (string-split n) )))

 (define (help lst)
   (if (empty? lst) (iter)

        (let ((s (string->list (car lst))))


    (cond ( (equal? #\% (car s)) (display (list-ref str (-(char->integer(cadr s)) 48)) out) (display " " out) (help (cdr lst)))
          (else (let ((a (reverse s)))
              (if (equal? (car a) #\%) (begin (display (list->string (reverse (cdr a))) out) (display " " out) (help (cdr lst)))
                                       (begin (display (car lst) out) (display " " out) (help (cdr lst))))))))))
  (iter))