用clojure实现《实用Common Lisp编程》中的简单数据库：CD数据库
(ns simple-cd-database.core)(defn make-cd [title artist rating ripped] {:title title :artist artist :rating rating :ripped ripped})(def db (atom []))(defn add-record [cd] (swap! db conj cd))(defn dump-db [] (doseq [cd @db] (doseq [[k v] cd] (prn k v)) (prn)))(add-record (make-cd "Home" "Dixie Chicks" 9 true))(add-record (make-cd "Love" "Dixie Chicks" 8 true));(prn @db)(dump-db);(prn @db)(defn prompt-read [promt] (print promt ": ") (flush ) (read-line))(defn y-or-n-p [string] (if (re-find #"(?i)y" string) true false))(defn parse-integer [str] (try (Integer/valueOf str) (catch NumberFormatException _ 0)))(defn prompt-for-cd [] (make-cd (prompt-read "Title") (prompt-read "Artist") (parse-integer (prompt-read "Rating")) (y-or-n-p (prompt-read "Ripped [y/n]"))))(defn add-cds [] (loop [_ (add-record (prompt-for-cd))] (if (y-or-n-p (prompt-read "Another? [y/n]")) (recur (prompt-for-cd)))));(add-cds );(dump-db)(defn save-db [file-name] (spit file-name (pr-str @db)))(defn load-db [filename] (reset! db (read-string (slurp filename))))(save-db "cd.txt")(load-db "cd.txt")(dump-db )(defn select [where-fn] (filter where-fn @db))(defn dis-select [where-fn] (drop-while where-fn @db))(defn where [& conditions] (fn [record] (let [condition-map (apply hash-map conditions)] (every? true? (for [ [condition value] condition-map] (= (condition record) value))))))(select (where :artist "Dixie Chicks"))(defn update [where-fn & new-value-map] (reset! db (map (fn [cd] (if (where-fn cd) (apply assoc cd new-value-map) cd)) @db)))(update (where :title "Home") :artist "big bang")(dump-db )