Cool.

(map second (s/exercise ::tic-tac-toe-board 3))

(["0" "1" "2"
  "3" "4" "X"
  "O" "X" "8"] ["O" "1" "2"
                "X" "O" "X"
                "X" "X" "O"] ["0" "1" "2"
                              "3" "4" "5"
                              "6" "7" "8"])