A-M baby

Task/Hailstone-sequence/Clojure/hailstone-sequence.clj

@@ -0,0 +1,17 @@
+(defn hailstone-seq [n]
+  (:pre [(pos? n)])
+  (lazy-seq
+   (cond (= n 1)   '(1)
+         (even? n) (cons n (hailstone-seq (/ n 2)))
+         :else     (cons n (hailstone-seq (+ (* n 3) 1))))))
+
+(def hseq27 (hailstone-seq 27))
+(assert (= (count hseq27) 112))
+(assert (= (take 4 hseq27) [27 82 41 124]))
+(assert (= (drop 108 hseq27) [8 4 2 1]))
+
+(let [{max-i :num, max-len :len}
+      (reduce #(max-key :len %1 %2)
+              (for [i (range 1 100000)]
+                {:num i, :len (count (hailstone-seq i))}))]
+  (println "Maximum length" max-len "was found for hailstone(" max-i ")."))