columns :: Board -> [[Cell]] 
columns b = [[b!!0, b!!3, b!!6],
            [b!!1, b!!4, b!!5],
            [b!!2, b!!5, b!!8]]
columns :: Board -> [[Cell]]
columns b = [[b!!0, b!!3, b!!6],
            [b!!1, b!!4, b!!5],
            [b!!2, b!!5, b!!8]]
columns b = [[b!!0, b!!3, b!!6],
            [b!!1, b!!4, b!!5],
            [b!!2, b!!5, b!!8]]