basics:
	(println "hello world")
	extension: .clj
	list: (list a b c) or '(a b c)
	symbols: 'x x (def x sth)
	keywords: :keyword
	vectors: [] [1 2 3] or (vector 1 2 3) no operations and different performance
	maps:
		(def map {"a" 1, "b" 2})
		(get map "a") returns 1
		(def map {:a 1, :b 2})
		(:a map) returns 1
	defining variables:
		(def x 5)
	anonymous functions:
		((fn [args] (expr)) args)
	functions:
		objects that can be called
		(defn funcname [args] expressions)
		same as (def funcname (fn [args] expressions))
		with documentation:
			(defn func "doc" [args] expressions)
			or (defn func {:doc "doc"} [args] expr)
	documentation:
		(doc form)
	if:
		(if true "yes")
		(if "" "yes") returns "yes"
	when:
		no else, many expressions
		(when true expr1 expr2 ...)
	let:
		temporary values to use inside
		(let [color "red" phrase (str "color is: " color)] (str "Clojure says: " phrase))
	java integration:
		instantiate: (new Object arg1 arg2 ...)
		call: (. (new Object) (methodname arg1 arg2 ...))
		import: (import '(package Class1 Class2))
	loops:
		(loop [i 0] (when (< i 5) expr1 expr2 (recur (inc i))))
		(dorun (for [i (range 0 5)] expr))
		(doseq [i (range 0 5)] expr)

functions:
	first
	rest
	concatenate: str
	+
	=

sequences:
	(seq [1 2 3])
	(cons 1 [2 3])