將*DB*中的資料資訊儲存到檔案中，以及可以從檔案中讀取資料資訊放置到*DB*全域性變數中

新增兩個函式 save-db 及 load-db

;使用全域性變數記錄資料
(defvar *db* nil)

;資料記錄格式
(defun make-cd (title artist rating ripped)
  (list :title title :artits artist :rating rating :ripped ripped)
)

;新增記錄
(defun add-record (cd)
 ( push cd *db*)
)

;檢視資料庫內容
(defun dump-db()
  (dolist (cd *db*)
    (format t "~{~a: ~10t~a~%~}~%" cd))
)

;提示使用者輸入CD資訊
(defun prompt-read (prompt)
  (format *query-io* "~a: " prompt)
  (force-output *query-io*)
  (read-line *query-io*)
)

;依次提示使用者輸入資訊
(defun prompt-for-cd()
  (make-cd
   (prompt-read "Title")
   (prompt-read "Artist")
   ;(prompt-read "Rating")
   ;(prompt-read "Ripped [y/n]")

   ;快餐式驗證資料有效性
   (or (parse-integer (prompt-read "Rating") :junk-allowed t) 0)
   (y-or-n-p "Ripped [y/n]: ")

  )
)

;批量新增資料，使用回車退出
(defun add-cds()
  (loop (add-record (prompt-for-cd))
     (if (not (y-or-n-p "Another? [y/n]:"))
	 (return)
      )
   )
)

;儲存資料
(defun save-db (filename)
  (with-open-file(out filename :direction :output :if-exists :supersede)
    (with-standard-io-syntax(print *db* out))
   )
)

;載入資料
(defun load-db(filename)
  (with-open-file(in filename)
    (with-standard-io-syntax(setf *db* (read in)))
   )
)
 

(save-db "d:/1.db")
(load-db "d:/1.db")