wc.clj

(ns wc.core
  (:require [clojure.core.reducers :as r]))

(defn char-counter [key init pred]
  (fn [reducing-fn]
    (fn
      ([acc]
       (reducing-fn acc))
      ([acc c]
       (reducing-fn (if (pred c)
                      (update acc key (fnil inc init))
                      acc) c)))))

(defn word-count [reducing-fn]
  (let [in-word (volatile! false)]
    (fn
      ([acc]
       (reducing-fn acc))
      ([acc c]
       (reducing-fn (cond
                      (#{\tab \newline \space} c)
                      (do (vswap! in-word not)
                          acc)
                      (not @in-word)
                      (do (vswap! in-word not)
                          (update acc :word-count (fnil inc 0)))
                      :else acc)
                    c)))))

(def xform (comp (char-counter :line-count 1 #{\newline}) 
                 (char-counter :char-count 0 (constantly true))
                 word-count))

(defn summarizer [acc _] acc)

(transduce xform (completing (r/monoid summarizer (constantly {}))) "lol\nfoo")