Haskell Guard Syntax
        checkDigit s 
                 | s == '0' = True
                 | s == '1' = True
                 | s == '2' = True
                 | otherwise = False

        --Guards in Haskell
        myGuards x 
                | x < 0 = -1
                | x > 0 = 1
                | otherwise = 0