a scruffy implementation of a function to pivot on a predicate

pivot-on.clj

(defn pivot-on 
    "This is about the worst way you could ever write this"
    [p coll] 
    (first (reduce (fn [[[l r] pivoted] v]
                     (if pivoted                    
                       [[l (conj r v)] true]
                       (if (p v)
                         [[l r] true]
                         [[(conj l v) r] false]))) 
                   [[[] []] false] 
                   coll)))



(defn pivot-on-2
  [p coll]
  (loop [[h & r] coll
         left    []]
    (if (p h) 
      [left r]
      (recur r (conj left h)))))


;; amalloy's version
(defn pivot-with 
  [pred seq]
  (let [seq (drop-while pred seq)] 
    (take-nth 2 (partition-by (comp boolean pred) seq))))