(defn unfold
([grow seed]
(lazy-seq
(if-let [[elt next-seed] (grow seed)]
(cons elt (unfold grow next-seed)))))
([grow finished? seed]
(unfold #(when (not (finished? %)) (grow %)) seed)))
(unfold (fn [x] [(* x x) (inc x)]) #(> % 10) 0)
(0 1 4 9 16 25 36 49 64 81 100)
(unfold (fn [x] (when (<= x 10) [(* x x) (inc x)])) 0)
(0 1 4 9 16 25 36 49 64 81 100)
I think it can be proved that any sequence can be build with a call to unfold.
Which makes it useful and solves the
"why reduce is not lazy?" question.
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