March 2014 update

Task/Subtractive-generator/Clojure/subtractive-generator.clj

@@ -0,0 +1,22 @@
+(defn xpat2-with-seed
+  "produces an xpat2 function initialized from seed"
+  [seed]
+  (let [e9 1000000000
+        fs (fn [[i j]] [j (mod (- i j) e9)])
+        s (->> [seed 1] (iterate fs) (map first) (take 55) vec)
+        rinit (map #(-> % inc (* 34) (mod 55) s) (range 55))
+        r-atom (atom [54 (int-array rinit)])
+        update (fn [[nprev r]]
+                  (let [n (-> nprev inc (mod 55))
+                        rx #(get r (-> n (- %) (mod 55)))
+                        rn (-> (rx 55) (- (rx 24)) (mod e9))
+                        _ (aset-int r n rn)]
+                    [n r]))
+        xpat2 #(let [[n r] (swap! r-atom update)]
+                (get r n))
+        _ (dotimes [_ 165] (xpat2))]
+    xpat2))
+
+(def xpat2 (xpat2-with-seed 292929))
+
+(println (xpat2) (xpat2) (xpat2)) ; prints: 467478574 512932792 539453717