Exercism: "Phone Number in Clojure"

This is my solution to the Phone Number problem in Clojure:

The first version:

	(ns phone)
	(defn extract-digits [phone-number]
	(let
	[digits (filter #(Character/isDigit %) phone-number)
	digits-length (count digits)]
	(cond
	(= digits-length 10) digits
	(and (= digits-length 11)
	(= (first digits) \1)) (rest digits)
	:else (repeat 10 0))))
	(defn number [phone-number]
	(apply str (extract-digits phone-number)))
	(defn area-code-digits [phone-number]
	(take 3 (extract-digits phone-number)))
	(defn area-code [phone-number]
	(apply str (area-code-digits phone-number)))
	(defn pretty-print [number-to-print]
	(let
	[digits (extract-digits number-to-print)]
	(apply str
	(concat "(" (area-code-digits digits) ") "
	(drop 3 (take 6 digits))
	"-"
	(drop 6 (take 10 digits))))))

view raw phone1.clj hosted with ❤ by GitHub

And then a second one:

	(ns phone)
	(defn extract-digits [phone-number]
	(let
	[digits (filter #(Character/isDigit %) phone-number)
	digits-length (count digits)]
	(cond
	(= digits-length 10) digits
	(and (= digits-length 11)
	(= (first digits) \1)) (rest digits)
	:else (repeat 10 0))))
	(def to-str
	(partial apply str))
	(def number
	(comp to-str extract-digits))
	(def area-code-digits
	(comp (partial take 3) extract-digits))
	(def area-code
	(comp to-str area-code-digits))
	(def extension-digits
	(comp (partial drop 3) (partial take 10)))
	(defn pretty-extension [extension-digits]
	(to-str
	(concat
	(take 3 extension-digits)
	"-"
	(drop 3 extension-digits))))
	(defn pretty-area-code [area-code]
	(to-str "(" area-code ")"))
	(defn pretty-print [number-to-print]
	(let
	[digits (extract-digits number-to-print)]
	(to-str
	(pretty-area-code (area-code digits))
	" "
	(pretty-extension (extension-digits digits)))))

view raw phone2.clj hosted with ❤ by GitHub

In this second version I removed some duplication with the help of the partial and comp functions and I also tried to make the code more readable by introducing several new helper functions.

You can nitpick my solution here or see all the exercises I've done so far in this repository.