FatePercentages.clj

(defn roll-fate-die []
  (- (rand-int 3) 1))

(defn test-fate-percentages [rolls-count]
  (let [rolls  (map (fn [x]
                      (reduce + (map (fn [x] (roll-fate-die))
                                     (range 4))))
                    (range rolls-count))]
    (map (fn [x] [(first x)
                 (int (* 100 (/ (count (second x)) rolls-count)))])
         (group-by (fn [x] x) rolls))))
(test-fate-percentages 100000)
;; => ([-1 19] [0 23] [1 19] [-2 12] [2 12] [-3 4] [3 4] [-4 1] [4 1])