fun.clj

;; currying! returns a partially evaluated function
(defn dice [size] (fn [] (+ 1 (rand-int size)))) ;; idiomatic vs using a rand formula

(def d20 (dice 20))

(defn roll-die-until-twenty
  ([die] (roll-die-until-twenty die 1)) ;; multiple arity
  ([die attempt]
     (let [roll (die)] ;; scoped binding, available only in this lexical scope
       (cond ;; https://clojuredocs.org/clojure.core/cond
          (= roll 20) attempt
          :else (roll-die-until-twenty die (inc attempt))))))

(defn experiment
  []
  (roll-die-until-twenty d20))

(defn average-of-results
  [results]
  (/ (reduce + results) (count results)))

(defn print-report
  [average]
  (println (format "Average: %f", (float average)))) ;; string interpolation!

(let [results (repeatedly 120000 #(experiment))] ;; no longer crashes at 7500 ~> n <~ 8000 ! :)
  (print-report (average-of-results results)))