Morpion clojure core

(ns morpion.core
  (:gen-class))

(defn -main
  []
  (let [frame ('morpion.graphic/make-frame)]
        (.setVisible frame true)
    )
)

(defn is-board?
    "Says whether the board is well defined :
  it must be a vector which has three vectors of three values
  (whatever they are, but you should avoid collections)."
    [board]
    (and
        (vector? board)
        (= 3 (count board))
      (every? true? (map vector? board))
      (every? #(= 3 (count %)) board)
    )
)


(defn board-str
    "Gets the board representation.
    Board must be a collection of 3 collections of 3 values.
    :cross or :circle are players values, any other value define blank."
  [board] {:pre [(is-board? board)]}
  (with-out-str
     (doseq [line board]
        (doseq [elem line]
           (print ({:cross \X, :circle \O} elem \_))
        )
        (newline)
     )
  )
)

(defn is-a-player-piece?
    "Says whether the given value is a player piece value :
    if it is either :cross or :circle."
    [value]
    (some #(= value %) '(:cross :circle))
)

(defn valid-coords?
    "Says whether a coords map is valid :
     it should have both :x and :y integers values,
     and both should be in [0,3[ (3 is excluded)."
    [coords]
    (and
        (map? coords)
        (:x coords) (integer? (:x coords)) (>= (:x coords) 0) (< (:x coords) 3)
        (:y coords) (integer? (:y coords)) (>= (:y coords) 0) (< (:y coords) 3)
    )
)

(defn cell-played?
    "Says whether the cell of the given coords (a map with :x and :y keys, and integers values)
    in the given board has either a :cross or a :circle value."
    [board coords] {:pre [(is-board? board) (valid-coords? coords)]}
    (let [value ( (board (:y coords)) (:x coords) )]
        (is-a-player-piece? value)
    )
)


(defn play-board
    "Tries to set the given value (either :cross or :circle), at the given coords
   (a map with :x and :y keys, and integers values),
  in the given board.
  Only fails if either :circle or :cross is already set for the given cell.
  Returns the modified board."
    [board coords value]
    {:pre [(is-board? board)
                 (is-a-player-piece? value)
                 (valid-coords? coords)]}
    (if (cell-played? board coords)
            board
            (let [line-to-modify (board (:y coords))
                        modified-line (assoc line-to-modify (:x coords) value)]
                (assoc board (:y coords) modified-line)
            )
    )
)

(defn new-board
    "Returns an empty board."
    []
    (vec (repeat 3 (vec (repeat 3 :none)) ))
)