->, ->> and thread-it

One guy suggested to use -> macro as often as possible instead of ->>. However, his final code doesn't look as clear as it should be (yes, it *should* be: we're coding in clojure).

I think, this is a great opportunity to use wonderful thread-it macro from "Clojure in Action" book:

	(defmacro thread-it [& [first-expr & rest-exprs]]
	(if (empty? rest-exprs)
	first-expr
	`(let [~'it ~first-expr]
	(thread-it ~@rest-exprs))))
	(def jay {:name "jay fields" :employer "drw.com" :current-city "new york"})
	(def john {:name "john dydo" :employer "drw.com" :current-city "new york"})
	(def mike {:name "mike ward" :employer "drw.com" :current-city "chicago"})
	(def chris {:name "chris george" :employer "thoughtworks.com" :current-city "new york"})
	(thread-it
	[jay john mike chris]
	(filter (comp (partial = "new york") :current-city) it)
	(group-by :employer it)
	(update-in it ["drw.com"] (partial map :name)))
	=>
	{"drw.com" ("jay fields" "john dydo"),
	"thoughtworks.com"
	[{:name "chris george",
	:current-city "new york",
	:employer "thoughtworks.com"}]}

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