(let* ((ser (with-input-from-file "state.scm"
             (lambda () (read))))
       (obj (u8vector->object ser)))
  (cond
    ((game-state? obj
     obj)
    ((game-state-1? obj)
     (game-state-from-v1 obj))
    ((game-state-2? obj)
     (game-state-from-v2 obj))
    (else
     (raise "This is not a game state!"))))