(defun check (filename)
  (let
    (
      (file (open filename))
    )
    (check-file file 0)
  )
)

(defun check-file (file level)
  (let
    (
      (ch (read-char file nil :eof))
    )
    (if
      (eq ch :eof)
      (if
	(eq level 0)
	(format nil "All good! You're a bracket matching god.")
	(if
	  (> level 0)
	  (format nil "You have ~D too many OPEN parentheses." level)
	  (format nil "You have ~D too many CLOSE parentheses." (- level))
	)
      )
      (cond
	(
	  (eq ch #\()
	  (check-file file (+ level 1))
	)
	(
	  (eq ch #\))
	  (check-file file (- level 1))
	)
	(
	  't
	  (check-file file level)
	)
      )
    )
  )
)