Common Lisp译本笔记2之第三章：简单的数据库实现(源码)

源代码：

;;定义一个全局变量，用于存放数据(defvar *db* nil);;制作一个CD需要的信息(defun make-cd (title artist rating ripped)  (list :title title :artist artist :rating rating :ripped ripped));;将一条CD信息记录到全局变量中(defun add-record (cd) (push cd *db*));;格式化输出数据(defun dump-db ()  (format t "~{~{~A: ~10t~A~%~}~%~}" *db*));;交互信息(defun prompt-read (prompt)  (format *query-io* "~A: " prompt)  (force-output *query-io*)  (read-line *query-io*));;交互获取CD信息(defun prompt-for-cd ()  (make-cd   (prompt-read "Title")   (prompt-read "Artist")   (or (parse-integer (prompt-read "Rating") :junk-allowed t) 0)   (y-or-n-p "Ripped [y/n]: ")));;添加任意个CD信息(defun add-cds ()  (loop (add-record (prompt-for-cd))     (if (not (y-or-n-p "Another? [y/n]: ")) (return))));;将所有CD信息保存到文件中(defun save-db (filename)  (with-open-file (out filename       :direction :output       :if-exists :supersede)    (with-standard-io-syntax      (print *db* out))));;加载文件中的CD信息(defun load-db (filename)  (with-open-file (in filename)    (with-standard-io-syntax      (setf *db* (read in)))));;通用查询(defun select (selector-fn)  (remove-if-not selector-fn *db*));;根据artist查询(defun artist-selector (artist)  #'(lambda (cd) (equal (getf cd :artist) artist)));;比较根据键比较值(defun make-comparison-expr (field value)  `(equal (getf cd ,field) ,value));;循环比较(defun make-comparisons-list (fields)  (loop while fields     collecting (make-comparison-expr (pop fields) (pop fields))));;定义一个where宏(defmacro where (&rest clauses)  `#'(lambda (cd) (and ,@(make-comparisons-list clauses))));;删除函数(defun delete-rows (selector-fn)  (setf *db* (remove-if selector-fn *db*)))

在eamcs中使用C-x C-f新建一个文件，输入文件名之后回车。

将上述源代码粘贴复制到此文件中，使用C-x C-s保存文件。

保存完成之后，在emacs中使用M-x输入slime回车，启动REPL(lisp环境)。

在REPL中输入：(load   "CD.lisp")回车，加载保存的文件。

到这一步，则可使用上述源码中的所有函数，接下来进行测试。

测试代码如下：

CL-USER> *db*NILCL-USER> (add-cds)Title: BangBomArtist: AreRating: 5Ripped [y/n]:  (y or n) yAnother? [y/n]:  (y or n) yTitle: So happyArtist: BreRating: 8Ripped [y/n]:  (y or n) nAnother? [y/n]:  (y or n) nNILCL-USER> (dump-db)TITLE:    So happyARTIST:   BreRATING:   8RIPPED:   NILTITLE:    BangBomARTIST:   AreRATING:   5RIPPED:   TNILCL-USER> (save-db "CD.db")((:TITLE "So happy" :ARTIST "Bre" :RATING 8 :RIPPED NIL) (:TITLE "BangBom" :ARTIST "Are" :RATING 5 :RIPPED T))CL-USER> (select (where :title "BangBom"))((:TITLE "BangBom" :ARTIST "Are" :RATING 5 :RIPPED T))CL-USER> (select (where :artist "Bre"))((:TITLE "So happy" :ARTIST "Bre" :RATING 8 :RIPPED NIL))CL-USER>