(define ((make-port-for-each read-function) function port)
  (do ((thing (read-function port) (read-function port)))
      ((eof-object? thing))
      (function thing)))

(define ((make-current-port-for-each read-function) function)
  (do ((thing (read-function) (read-function)))
      ((eof-object? thing))
      (function thing)))

(define ((make-line-by-line-transform function))
  ((make-current-port-for-each read-line)
   (lambda (string) (display (function string)) (newline))))

(define ((make-rederected-transform transform) in-filename out-filename)
  (with-output-to-file
    out-filename
    (lambda ()
      (with-input-from-file
        in-filename
        transform))))

(define downcase-transform (make-line-by-line-transform string-downcase!))

(define file-downcase (make-rederected-transform downcase-transform))

(define identity-transform (make-line-by-line-transform identity))

(define copy-file (make-rederected-transform identity-transform))

(define (display-file file-name)
  (with-input-from-file
    file-name
    identity-transform))

(define ((make-file-transform-by-lines! function) filename)
  (define list '())
  (with-input-from-file
    filename
    (lambda ()
      (set! 
        list ((make-collect-cons (make-port-for-each read-line))
              function
              (current-input-port)))))
  (with-output-to-file
    filename
    (lambda () (for-each (lambda (x) (display x) (newline)) list))))

(define file-downcase! (make-file-transform-by-lines! string-downcase!))