My first Clojure program

main.clj

; clojure -M main.clj 3
; 000
; 001
; 010
; 011
; 100
; 101
; 110
; 111

(defn binary-strings [level]
  (def bits ["0" "1"])
  (cond
    (< level 0) (throw (AssertionError. "Expected a non-negative integer"))
    (= level 0) []
    (= level 1) bits
    (> level 1) (for [x bits y (binary-strings (dec level))] (str x y))
  )
)

(def level (parse-long (first *command-line-args*)))
(run! println (binary-strings level))