Read a very large text file into a list in clojure

Question

What is the best way to read a very large file (like a text file having 100 000 names one on each line) into a list (lazily - loading it as needed) in clojure?

Basic

Answer 1

Andrew's solution worked well for me, but nested defns are not so idiomatic, and you don't need to do lazy-seq twice: here is an updated version without the extra prints and using letfn:

(defn lazy-file-lines [file]
  (letfn [(helper [rdr]
                  (lazy-seq
                    (if-let [line (.readLine rdr)]
                      (cons line (helper rdr))
                      (do (.close rdr) nil))))]
         (helper (clojure.java.io/reader file))))

(count (lazy-file-lines "/tmp/massive-file.txt"))
;=>