Clojure: reduce, reductions and infinite lists

Question

Reduce and reductions let you accumulate state over a sequence. Each element in the sequence will modify the accumulated state until the end of the sequence is reached.

Answer 1

If you want to keep getting items from a list like an IO stream and keep state between runs, you cannot use doseq (without resorting to def's). Instead a good approach would be to use loop/recur this will allow you to avoid consuming too much stack space and will let you keep state, in your case:

 (loop [c (cycle [0])]
   (if (evaluate-some-condition (first c))
     (do-something-with (first c) (recur (rest c)))
     nil))

Of course compared to your case there is here a condition check to make sure we don't loop indefinitely.