Clojure eager concatenation

eager-cat.clj

(defn eager-cat
  "Eager concat.
  Doesn't blow up the stack.
  Returns a vector."
  ([]
   [])
  ([xs]
   (vec xs))
  ([xs ys]
   (into (vec xs) ys))
  ([xs ys & more]
   (reduce eager-cat
           xs
           (cons ys more))))