lisp - 格式化 Practical Common LISP 的第一个练习时出现问题

Question

我开始学习 Practical Common LISP，第一个练习是写一个 simple database .我在 cygwin 上使用 GNU CLISP 2.48 (2009-07-28)。

这段代码，我已经多次与书中进行了比较，并没有按照书中所说的那样产生输出

(defun make-cd (title artist rating ripped)
  (list :title title :artist artist :rating rating :ripped))
(defvar *db* nil)
(defun add-record (cd) (push cd *db*))
(add-record (make-cd "Roses" "Kathy Mattea" 7 t))
(add-record (make-cd "Fly" "Dixie Chicks" 8 t))
(add-record (make-cd "Home" "Dixie Chicks" 9 t))
(defun dump-db ()
  (dolist (cd *db*)
   (format t "~{~a:~10t~a~%~}~%" cd)))

(dump-db)

我明白了

TITLE:    Home
ARTIST:   Dixie Chicks
RATING:   9
RIPPED:   
*** - There are not enough arguments left for this format directive.
      Current point in control string:
        "~{~a:~10t~a~%~}~%"
                  |

我对 format 或 LISP 的理解不够深入，无法进行故障排除。这本书说我应该得到数据库中所有记录的列表。出了什么问题？

Answer 1

首先，让我们看一下(make-cd)的返回:

[12]> (make-cd "Home" "Dixie Chicks" 9 t)
(:TITLE "Home" :ARTIST "Dixie Chicks" :RATING 9 :RIPPED)

您没有包含 :ripped 的值!将 (make-cd) 更改为:

(defun make-cd (title artist rating ripped)
  (list :title title :artist artist :rating rating :ripped ripped))

注意 :ripped 之后的 ripped。