into-str.clj

;; thanks ghadi from #clojure.beginners

(defn into-str
  "reduce coll into a String, given a transducer"
  [xf coll]
  (transduce (comp xf (map str))
             (fn
               ([] (StringBuilder.))
               ([^StringBuilder sb] (.toString sb))
               ([^StringBuilder sb s] (.append sb ^String s)))
             coll))