title: Make String from Sequence of Characters
body: <p>This code does not work as I expected. Could you please explain why?</p>
  
  <pre><code>(defn make-str [s c]
      (let [my-str (ref s)]
      (dosync (alter my-str str c))))
  
  (defn make-str-from-chars
      "make a string from a sequence of characters"
      ([chars] make-str-from-chars chars "")
      ([chars result]
          (if (== (count chars) 0) result
          (recur (drop 1 chars) (make-str result (take 1 chars))))))
  </code></pre>
  
  <p>Thank you!</p>