Short-circuiting version of reduce - see http://jkkramer.wordpress.com/2011/03/29/clojure-python-side-by-side/

reduce-true.clj

(defn tails [s]
  "The sequence of sequences starting at each position in the given sequence 's'."
  (lazy-seq (when-let [s (seq s)]
              (cons s (tails (rest s))))))

(defn reduce-true [f val coll]
  "A short-circuiting version of 'reduce'. Stops evaluation when the
  accumulated value is logically false."
  (let [v (->> (reductions f val coll)
               (tails)
               (take-while first)
               (last))]
    (if (empty? (rest v)) (first v))))