examples/naughts_and_crosses.py
def make_move(self, x, y):
        '''Return a board with a cell filled in by the current player. If
        the cell is already occupied then return the board unchanged.'''
        if self.board[y][x] == ' ':
            return lens.board[y][x].set(self.player)(self)
        return self
def make_move(self, x, y):
        '''Return a board with a cell filled in by the current player. If
        the cell is already occupied then return the board unchanged.'''
        if self.board[y][x] == ' ':
            return lens.board[y][x].set(self.player)(self)
        return self
Return a board with a cell filled in by the current player. If
        the cell is already occupied then return the board unchanged.