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(def almost-stats-graph
  {:n  (fn [xs]   (count xs))
   :m  (fn [xs n] (/ (sum identity xs) n))
   :m2 (fn [xs n] (/ (sum #(* % %) xs) n))
   :v  (fn [m m2] (- m2 (* m m)))})

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;; Take a map {:xs xs} and return a map
;; of simple univariate statistics of xs
(defn stats [{:keys [xs]}]
  (let [n  (count xs)
        m  (/ (sum identity xs) n)
        m2 (/ (sum #(* % %) xs) n) 
        v  (- m2 (* m m))]
    {:n n   ; count   
     :m m   ; mean 
     :m2 m2 ; mean square

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(defmacro <- [& body]
  `(-> ~(last body) ~@(butlast body)))

(deftest <--test
  (is (= [2 3]
         (-> {1 1}
             (assoc 3 4)
             (update-in [1] inc)
             (->> (map-vals dec)
                  (map-keys inc)

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(def fib-var-obj 
  (fn [x]
    (if (< x 2)
      1
      (+ (fib-var-obj (- x 1))
         (fib-var-obj (- x 2))))))

(defn fib-lex-obj [x]
  (if (< x 2)
    1