Difference between iterate and repeatedly applying a function

Question

I'm studying the Clojure Koans:

https://github.com/functional-koans/clojure-koans/blob/master/src/koans/10_lazy_sequences.clj

I am stuck on this one:

"Iteration can be used for repetition"
  (= (repeat 100 :foo)
     (take 100 (iterate ___ :foo)))

I don't know the exact builtin function to fill in the _ blanks with, so I tried writing my own. I wrote it as a separate function as a test.

I intend this one to be: if x is a seq, then just repeat its first element. Otherwise, make it a seq.

(def f (fn [x] (if (seq? x) (cons (first x) x) (cons x '()))))

When I run it explicitly, it looks fine:

user=> (f :abc)
(:abc)
user=> (f (f :abc))
(:abc :abc)
user=> (f (f (f :abc)))
(:abc :abc :abc)

But using iterate adds an extra parenthesis:

user=> (take 1 (iterate f :abc))(:abc)
user=> (take 2 (iterate f :abc))
(:abc (:abc))
user=> (take 3 (iterate f :abc))
(:abc (:abc) (:abc :abc))

What causes this?

Answer 1

(fn [x] x)

solves this particular koan