Handling stdin Clojure

The below doesn't seem to work, but I'm not quite sure why. All move-board does is take in a 2D array and return a 2D array, rest of the code is all there. Basically I'm trying to accomplish something like the following python:

While True:
  do stuff
  if gameover:
    print("Game Over!")
    break

Clojure that isn't working (prints board once, asks for input, then hangs)

(defn game-loop [board]
  (loop [b board]
    (if (game-over? b) "Game Over!"
        (do (print-board b)
            (recur (move-board (read-line) b))))))

Solution

We would need to see what your other functions are doing. I fabricated them minimally to what seems likely, and reindented to make the if-branch clearer. Your loop also was unnecessary.

(defn game-over? [b] false)
(defn print-board [b] (println b))
(defn move-board [ln b] (println "moving board:" ln))

(defn game-loop [b]
  (if (game-over? b)
    "Game Over!"
    (do (print-board b)
        (recur (move-board (read-line) b)))))

(game-loop :bored)

With those top three functions, your loop behaves as expected: prompting for a single line, infinitely. Well, at least the first time, but then your "hang" issue is reproduced.

This is likely being caused by this issue with the JVM. Also discussed here.