take_to_and_partition_after.clj

;; Gathers values up to (and including) the one for
;; which the predicate fails.
(defn take-to
  [pred coll]
  (when-let [s (seq coll)]
    (let [[x & xs] s]
      (if-not (pred x)
        (list x)
        (lazy-cat (cons x (take-to pred xs)))))))

;; Partitions the sequence based on a predicate. Includes
;; the first value where the predicate fails in the sequence.
;; Heavily influenced by partition-by from clojure.core.
(defn partition-after
  [pred coll]
  (lazy-seq
   (when-let [s (seq coll)]
     (let [fst (first s)
           fv (pred fst)
           run (cons fst (take-to #(= fv (pred %)) (rest s)))]
       (cons run (partition-after pred (drop (count run) s)))))))