How to generate repeatable random sequences with rand-int

Question

I want to be able to generate repeatable numbers using rand in Clojure. (Specifically, I want results of calls to rand-nth or Incanter\'s sample

Answer 1

In the original question, two things are misunderstood:

• How to use dynamic vars
• How to use clojure.data.generators

First, dynamic vars should be managed via the binding macro. Second rand is not a function of clojure.data.generators, but of clojure.core itself and thus resetting the *rnd* var doesn't have effect. So here is how you should do it:

(require '[clojure.data.generators :as gen])

(binding [gen/*rnd* (java.util.Random. 437)]
  (println (gen/double)) ;=> 0.7634858067742888
  (println (gen/double)) ;=> 0.6959205688388975
  )

(binding [gen/*rnd* (java.util.Random. 437)]
  (println (gen/double)) ;=> 0.7634858067742888
  (println (gen/double)) ;=> 0.6959205688388975
  )