clojure的文件IO处理的持续优化

、需求，把文本文件r.txt的内容处理（每行前边加hello 后边加！），然后写入w.txt
2、实现1：
(defn read-file []
    (with-open [rdr (clojure.java.io/reader "f:/r.txt")]
        (doall
            (map #(str "hello" % "!") (line-seq rdr)))))
(defn write-file []
      (with-open [w (clojure.java.io/writer "f:/w.txt" :append true)]
        (binding [*out* w]
            (doseq [line (read-file )]
                (println line)))))
(write-file)
实现2：

(defn read-file []
    (with-open [rdr (clojure.java.io/reader "f:/r.txt")]
        (apply str
            (map #(str "hello" % "!") (line-seq rdr)))))
(defn write-file []
      (with-open [w (clojure.java.io/writer "f:/w.txt" :append true)]
          (.write w (read-file))))
(write-file)
实现3：

(defn read-file []
    (with-open [rdr (clojure.java.io/reader "f:/r.txt")]
        (apply str
            (map #(str "hello" %  "!") (line-seq rdr)))))
(spit "f:/w.txt"  read-file :append true)

尤以后种方式最为精简。clojure魔力大大的！