My first clojure program!

guess.clj

(ns user)

(defn askForNumber
  "Asks for a number within a range, returning nil if input is not a number."
  [ low high ]
  (do
    (print (str "Pick a number from " low " to " high ": "))
    (flush)
    (let [ num (read-string (read-line))]
      (if (number? num) num nil))
))

(defn guess
  "Play the game with a given range and secret number."
  [low high answer]
  (let [num (askForNumber low high)]
    (case num
      nil (do
        (println "That's not a number!")
        (guess low high answer))
      (cond
        (= num answer) (println (str "You guessed it: the number was " answer "!"))
        (< num answer) (do
          (println "Too low!")
          (guess low high answer)
          )
        (> num answer) (do
          (println "Too high!")
          (guess low high answer)
          )))))

(defn main
  "Guess the secret number!"
  []
  (let [ low 1
          high 100
          answer (+ low (rand-int (- high low)))]
    (guess low high answer)))

; Call (main) in the repl to play!