Constrain a sequence in clojure

constrain.clj

(defn constrain
  "Truncate a sequence

  Returns a two-element vector to signal whether of not the seq has
  been truncated"
  [max coll]
  (let [[head tail] (split-at max coll)]
    (if (seq tail)
      [nil (take max coll)]
      [coll])))

;; usage

user=> (let [[a b] (constrain 5 (range 5))] (or a (conj (vec b) :...)))
(0 1 2 3 4)
user=> (let [[a b] (constrain 5 (range 6))] (or a (conj (vec b) :...)))
[0 1 2 3 4 :...]