safeDigitToInt :: Char -> Int
safeDigitToInt '.' = error "safeDigitToInt: '.' is not an allowed input."
safeDigitToInt :: Char -> Int
safeDigitToInt '.' = error "safeDigitToInt: '.' is not an allowed input."
safeDigitToInt '.' = error "safeDigitToInt: '.' is not an allowed input."