Exercism: "Word count in Clojure"

This is my solution to the Word count problem in Clojure:

	(ns word-count
	(:require [clojure.string :as str]))
	(defn word-count [sentence]
	(let
	[count-word-occurrences
	(fn [counted-words word]
	(let
	[add-new-word
	(fn [] (assoc counted-words word 1))
	add-occurrence-to-word
	(fn [] (assoc counted-words word
	(+ (get counted-words word) 1)))]
	(if (contains? counted-words word)
	(add-occurrence-to-word)
	(add-new-word))))
	extract-words-from
	(fn [sentence]
	(let
	[remove-punctuation (comp (partial apply str)
	(partial filter
	#(or (Character/isLetter %)
	(Character/isSpace %)
	(Character/isDigit %))))]
	(str/split
	(remove-punctuation
	(str/lower-case sentence)) #"\s+")))]
	(reduce
	count-word-occurrences
	{}
	(extract-words-from sentence))))

view raw word-count.clj hosted with ❤ by GitHub

I created some local helpers and played with partial and comp to make the code more readable.
I also reduced the number of parameters of some local helpers by using some free variables.

I really liked how the reduce function can be applied to a map data-structure in Clojure.

You can nitpick my code here.

--------------------------------

Update:

After learning some new stuff, I've been able to simplify the code a bit more:

	(ns word-count
	(:require [clojure.string :as str]))
	(defn- extract-words-from [sentence]
	(let
	[remove-punctuation
	(comp (partial apply str)
	(partial filter
	#(or (Character/isLetter %)
	(Character/isSpace %)
	(Character/isDigit %))))]
	(str/split (remove-punctuation (str/lower-case sentence)) #"\s+")))
	(defn word-count [sentence]
	(frequencies (extract-words-from sentence)))

view raw word-count1.clj hosted with ❤ by GitHub

I used the frequencies function to count each word frequency and the defn- special macro to make extract-words-from function private.

You can nitpick this new version here.