Clojureでランダムな文字列を生成してみる ref: http://qiita.com/kurogelee/items/e740d6251f87fb87b29b

file1.txt

user=> (range-size 50 5)
(50 51 52 53 54)
user=> (rand-str 20)
"195Tbl1nE8ME0QGEwJl7"
user=> (rand-str 20 "abc")
"cbabbbcabbbaaaabcaca"

rand-str.clj

(defn range-size
  ([start size] (range-size start size 1))
  ([start size step]
    {:pre[(integer? size)]}
    (take size (range start (+ start (* size step)) step))))

(defn rand-str
  ([n] (rand-str n (mapcat #(apply range-size %) [[48 10] [65 26] [97 26]])))
  ([n charseq] (apply str (map char (repeatedly n #(rand-nth charseq))))))