(do
  (def SMA
    (fn [length]
      (do
        (def history (series :float))
        (def sum 0.0)

		(fn [val]
           (do
             (def hist_len (len history))
             (if (>= hist_len length)
               (assign sum (- sum (history (- length 1)))))

  		      (push history val)
              (assign sum (+ sum val))

              (if (>= hist_len length)
                (/ sum length))
           )))))
)