wrap function in clojure based on Uncle Bob's http://blog.8thlight.com/uncle-bob/2013/01/07/FPBE3-Do-the-rules-change.html. I wrote this to provide a more readable and idiomatic version than what Uncle Bob presented.

wrap.clj

(use '[clojure.string :only (split)])

(defn break-long-word [n word]
   (if (> (count word) n)
     [(take n word) (break-long-word n (drop n word))]
     [word]))

(defn break-long-words [n words] 
  (mapcat #(break-long-word n %) words))

(defn combine-words [n [w1 w2 & words]]
  (cond (not w1) []
        (not w2) [w1]
        (>= (+ (count w1) (count w2)) n) (cons w1 (combine-words n (cons w2 words)))
        :else (cons (str w1 " " w2) (combine-words n words))))

(defn wrap [n i]
  (->> (split i #" ")
       (break-long-words n)
       (combine-words n)
       (interpose "\n")
       (flatten)
       (apply str)))