#lang scheme
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; 
;;;  A Very Simple Example of standard I/O
;;;  Author: Yilan Gu
;;;  CSC324 Lecture 6
;;;  Date: Oct. 15th, 2009
;;;  I/O details:
;;;  http://docs.plt-scheme.org/reference/input-and-output.html
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;



; Main loop of the example

(define in-out
  (lambda ()
    (menu)
    (let ((answer (read)))
      (cond
        ((eq? answer 1) (write "Hello World")
                        (newline)
                        (in-out))
        ((eq? answer 2) (display "Hello World")
                        (newline)
                        (in-out))
        ((eq? answer 3) (printf "~a as a string is ~s.~n"
                                '(3 4) "(3 4)")
                        (in-out))                                              
        ((eq? answer 4) (display "Thank you. Good bye !!"))
        (else (display "Bad choice. Try again.")
              (newline)
              (in-out))
        
        )
      
      )
    )
  )


(define menu
  (lambda ()
    (newline)
    (newline)
    (display " ----- 1.   show an example of write ------")
    (newline)
    (display " ----- 2.   show an example of display ------")
    (newline)
    (display " ----- 3.   show an example of printf ------")
    (newline)
    (display " ----- 4.   Quit ---------------")
    (newline)
    (newline)
    (display " *** Please chose an option ***")
    (newline)
    (newline)
    )
  )