How do I build up an array using let in Clojure?

(test [1 2 3]) is returning [], not [1 2 3], why?

(defn test [some-array]
      (let [x []]
        (doseq [i some-array]
          (conj x i))
        x))

(test [1 2 3])

EDIT: a comment below suggested I am trying an imperative approach with a functional language, and that's probably correct. What I am trying to do is build up a vector of vectors using an initial sequence of values (inside a vector in this case) as starting data. I guess I could try to transform each value in the vector and return it, but that seems harder conceptually (from an imperative mindset) than taking a starting vector and using it to build out a new one and return that.

As an example, suppose I had a function that takes 1 and returns "one", and I wanted to have a function take [1 2 3] and return [[1 "one"][2 "two"][3 "three"]].

Solution

Clojure's focus is on immutable data and functional programming. Your code there feels like you want to do some imperative style ideas here.

Your test there could as well be identity - a copy of some immutable data structure, is just the immutable data structure itself.

If your example there is oversimplified and you want to "append" to some x with data inside it, you could use into.

edit

To transform a sequence one-by-one (e.g. each input results in a different output), use map (or mapv to get a vector and make it eager). E.g.

(def numbers
  {1 "one"
   2 "two"
   3 "three"})

(defn test [some-array]
  (mapv #(vector % (numbers %)) some-array))

(println (test [1 2 3]))
; → [[1 one] [2 two] [3 three]]

(Bonus points for using juxt as mapping function)