title: Clojure: sequence back to vector
body: <p>How can I cast a sequence back to vector after a sequence producing operation (like sort)? Does using (vec..) on a sequence that was a vector is costly? </p>
  
  <p>One (bad?) possibility is creating a new vector out of sequence:</p>
  
  <pre><code>(vec (sort [1 2 3 4 5 6]))
  </code></pre>
  
  <p>I am asking because I need random access (nth ..) to huge sorted vectors - which are now huge sequences after the sort, with horrible O(n) random access time</p>