show instance

show.hs

instance Show ValidationError where
    show (SquareTaken x) = "Move #" ++ show (x + 1) ++ " is invalid - the square is already taken!"
    show (WrongPiece x expected actual) = "Wrong piece on move #" ++
                                    show (x + 1) ++
                                    ". Expected '" ++ show expected ++ "', got '" ++ show actual ++ "'."
    show (WrongName x expected actual) = "Wrong player name on move #" ++
                                show (x + 1) ++ ". Expected '" ++ expected ++ "', got '" ++ actual ++ "'."
    show WrongFirstMove = "X must make the first move."