Explicite iteration on CLR

explicite-iteration-clr.clj

(require '[clojure.clr.io :as io])

(def in-file "/path/to/datafile-4gb.tsv")
(def out-file "/path/to/datafile-16gb.tsv")

(defn multiply-string [s n]
  (cond
   (> n 1) (str s \newline (multiply-string s (dec n)))
   (= n 1) (str s \newline)
   :else nil))

(defn multiply-file [in out n]
  (with-open [reader (io/text-reader  in)             ; FB: io/reader
              writer (io/text-writer out)]            ; FB: io/writer
    (loop [line (.ReadLine reader)]                   ; FB: .readLine
      (if (nil? line)
          nil
          (do
            (.Write writer (multiply-string line n))  ; FB: .write
            (recur (.ReadLine reader)))))))           ; FB: .readLine


#'user/multiply-file
user=> (time (multiply-file in-file out-file 4))
"Elapsed time: 2638910 msecs"
nil