Given n, x, f: I want output of the form:
[x, f(x), f(f(x)), f(f(f(x))), ..., f^{n-1}(x)] This can be done via reductions
(reductions (fn [state _] (f state)) state (range n)) Is there a primitive that provides a shorter solution?
What you want is clojure.core/iterate, which provides f -> x -> [x, f(x), f^2(x), f^3(x), ...] and clojure.core/take which provides a way to slice the first n elements off of a sequence. take is lazy, as is iterate so there are no guarantees about side-effects.
iterate nor take are subject to chunking, so far as I can see from the source code. Nor can I see how you could implement iterate to take advantage of parallelism.
iterate isn't implemented as a chunked sequence, and (b) for arbitrary f, how would you compute f^n(x) without first computing f^(n-1)(x)?). If you feel otherwise, feel free to revert.
(take n (iterate f x)).