unfold in clojure as Stream.unfold in elixir

unfold.clj

(defn unfold 
  "Creates a lazy sequence based on start accumulator and step functon.
   The step function transform the state as below:
     step(value) -> [current-value, next-accumulator]
   For example:
        (unfold 5 (fn [n]
            (when-not (zero? n)
              [n (dec n)])))

  "
  [start step]
  (when start
    (lazy-seq
     (let [[cs ns] (step start)]
       (when cs
         (cons cs
               (lazy-seq (unfold ns step))))))))

(take 5 (unfold [0 1] (fn [[n1 n2]] [n1 [n2 (+' n1 n2)]])))
(unfold 5 (fn [n]
            (when-not (zero? n)
              [n (dec n)])))