Tuesday, 10 March 2009

Generate a random string in Clojure

In my quest to learn Lisp, I discovered Clojure, a List inspired language on the JVM. I really like it and hope to be able to use it more and more.
Here's a code snippet to generate a random string in Clojure. This is something I end up using a many projects. This is a version that is not made to be the shortest, but the most readable. And as you can see, access to Java's classes and libraries is very easy:


:use java's random generator
(def random (java.util.Random.))
;define characters list to use to generate string
(def chars 
   (map char (concat (range 48 58) (range 66 92) (range 97 123))))
;generates 1 random character
(defn random-char [] 
  (nth chars (.nextInt random (count chars))))
; generates random string of length characters
(defn random-string [length]
  (apply str (take length (repeatedly random-char))))


Suggestions to improve the code are welcome, I'm still a newbie in Lisp-style programming and Clojure!
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12 comments:

  1. Jeff2 May 2009 at 13:41

    A slightly modified version, without using Java's random and with corrected ranges for the characters. (Annoying that blogger won't allow code or pre tags...)

    (def VALID-CHARS
    (map char (concat (range 48 58) ; 0-9
    (range 66 91) ; A-Z
    (range 97 123)))) ; a-z

    (defn random-char []
    (nth VALID-CHARS (rand (count VALID-CHARS))))

    (defn random-str [length]
    (apply str (take length (repeatedly random-char))))

    ReplyDelete
  2. Aaron B. Iba5 August 2010 at 23:57

    Jeff, I think you meant:

    (range 65 91) ; A-Z

    Don't want to forget A!

    ReplyDelete
  3. Topher13 January 2011 at 03:31

    Jeff, your random-char function could be simplified like this:

    (defn random-char []
    (random-nth VALID-CHARS))

    ReplyDelete
  4. Jeff13 January 2011 at 09:25

    Yeah, now we can use rand-nth, but this function wasn't around when I first commented.

    ReplyDelete
  5. Filip25 May 2011 at 08:30

    This comment has been removed by the author.

    ReplyDelete
  6. Filip25 May 2011 at 08:30

    This is my version:

    (defn random-string [length]
    (let [ascii-codes (concat (range 48 58) (range 66 91) (range 97 123))]
    (apply str (repeatedly length #(char (rand-nth ascii-codes))))))

    ReplyDelete
  7. Rob1 October 2012 at 20:57

    Exactly what I was looking for, thanks!

    ReplyDelete
  8. Unknown9 February 2013 at 17:35

    UUID version:

    (defn new-uuid []
    (java.util.UUID/randomUUID))

    https://coderwall.com/p/dtw0sg

    ReplyDelete
  9. A Breaking Change9 June 2013 at 23:10

    (Integer/toString (.nextInt random) 36)

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  10. A Breaking Change9 June 2013 at 23:58

    Microsoft-style product keys

    (defn r1ss [] (clojure.string/upper-case (Integer/toString (.nextInt random Integer/MAX_VALUE) 36)))
    (defn r25s [] (->> (repeatedly r1ss)
    (apply concat)
    (take 25)
    (partition 5)
    (map (partial apply str))
    (interpose "-")
    (apply str)))

    ReplyDelete
  11. Inez23 September 2013 at 05:15

    Awesome!

    ReplyDelete
  12. Theresa25 September 2013 at 07:22

    This is gorgeous!

    ReplyDelete