/// <summary>Converts a Roman Numeral to its decimal representation</summary>
/// <exception cref="ArgumentException">Thrown when an illegal number is detected</exception>
public static int ToDecimal(string numeral)
{
int output = 0;
for (int i = 0; i < numeral.Length; i++)
{
int tmp = DigitConverter.NumeralToDigit(numeral[i]);
if (i < numeral.Length - 1)
{
int next = DigitConverter.NumeralToDigit(numeral[i + 1]);
if (next > tmp)
{
if (!(tmp == next / 5 || tmp == next / 10))
{
throw new ArgumentException($"Number {numeral} is illegal!");
}
output += next - tmp;
i++;
continue;
}
}
output += tmp;
}
return(output);
}
/// <summary>Converts a Decimal Number to a Roman Numeral</summary>
/// <exception cref="ArgumentException">Thrown when a Number is greater than 99999</exception>
public static string ToRoman(int number)
{
if (number > 999999)
{
throw new ArgumentException($"Number {number} is too big");
}
string output = string.Empty;
int[] digits = DigitConverter.SplitDigits(number);
for (int i = digits.Length - 1; i >= 0; i--)
{
int digit = digits[i];
output += DigitConverter.DigitToNumeral(digit, i);
}
return(output);
}
