Calculating the Moving Average of a List

Question

This weekend I decided to try my hand at some Scala and Clojure. I\'m proficient with object oriented programming, and so Scala was easy to pick up as a language, but wante

Answer 1

Here is Clojure pretending to be a more functional language. This is fully tail-recursive, btw, and includes leading zeroes.

(defn moving-average [period values]
  (loop [[x & xs]  values
         window    []
         ys        []]

    (if (and (nil? x) (nil? xs))
      ;; base case
      ys

      ;; inductive case
      (if (< (count window) (dec period))
        (recur xs (conj window x) (conj ys 0.0))
        (recur xs
               (conj (vec (rest window)) x)
               (conj ys (/ (reduce + x window) period)))))))

(deftest test-moving-average
  (is (= [0.0 0.0 0.0 4.75 5.0 6.0 7.25 8.0 8.25 6.5]
         (moving-average 4 [2.0 4.0 7.0 6.0 3.0 8.0 12.0 9.0 4.0 1.0]))))

Usually I put the collection or list parameter last to make the function easier to curry. But in Clojure...

(partial moving-average 4)

... is so cumbersome, I usually end up doing this ...

#(moving-average 4 %)

... in which case, it doesn't really matter what order the parameters go.