How do I filter elements from a sequence based on indexes

Question

I have a sequence s and a list of indexes into this sequence indexes. How do I retain only the items given via the indexes?

Simple example:

Answer 1

I know this is not what was asked, but after reading these answers, I realized in my own personal use case, what I actually wanted was basically filtering by a mask.

So here was my take. Hopefully this will help someone else.

(defn filter-by-mask [coll mask]
  (filter some? (map #(if %1 %2) mask coll)))

(defn make-errors-mask [coll]
  (map #(nil? (:error %)) coll))

Usage

(let [v [{} {:error 3} {:ok 2} {:error 4 :yea 7}]
    data ["one" "two" "three" "four"]
    mask (make-errors-mask v)]
    (filter-by-mask data mask))

; ==> ("one" "three")