roman numerals - it's ugly but it works

Roman numerals.swift

import Foundation

extension Int {

	subscript(digitIndex: Int) -> Int? {
		print(self)
		var decimalBase = 1
		for _ in 0..<digitIndex {
			decimalBase *= 10
		}
		return (self / decimalBase) % 10
	}

	func romanNumerals() -> String {
		var index = 0
		var out = ""
		while let value = self[index] {
			guard let tensPlace = TensPlace(rawValue: index) else {
				break
			}
			out = "\(romanNumeral(for: value, tensPlace: tensPlace))\(out)"
			index += 1
		}
		return out
	}

	private enum TensPlace: Int {
		case ones = 0
		case tens
		case hundreds
		case thousands
	}

	private func romanNumeral(for digit: Int, tensPlace: TensPlace) -> String {
		var out = ""
		switch tensPlace {
		case .ones:
			if digit < 4 {
				out = (0..<digit).map { _ in "I" }.joined()
			} else if digit == 4 {
				out = "IV"
			} else if digit < 9 {
				out = "V"
				out += (5..<digit).map { _ in "I" }.joined()
			} else {
				out = "IX"
			}
		case .tens:
			if digit < 4 {
				out = (0..<digit).map { _ in "X" }.joined()
			} else if digit == 4 {
				out = "XL"
			} else if digit < 9 {
				out = "L"
				out += (5..<digit).map { _ in "X" }.joined()
			} else {
				out = "XC"
			}
		case .hundreds:
			if digit < 4 {
				out = (0..<digit).map { _ in "C" }.joined()
			} else if digit == 4 {
				out = "CD"
			} else if digit < 9 {
				out = "D"
				out += (5..<digit).map { _ in "C" }.joined()
			} else {
				out = "CM"
			}
		case .thousands:
			out = (0..<digit).map { _ in "M" }.joined()
		}
		return out
	}
}


1.romanNumerals()
3.romanNumerals()
4.romanNumerals()
5.romanNumerals()
8.romanNumerals()
9.romanNumerals()

11.romanNumerals()
32.romanNumerals()
42.romanNumerals()
55.romanNumerals()
74.romanNumerals()
98.romanNumerals()

101.romanNumerals()
202.romanNumerals()
402.romanNumerals()
445.romanNumerals()
853.romanNumerals()
911.romanNumerals()
999.romanNumerals()

1002.romanNumerals()
3052.romanNumerals()
9004.romanNumerals()