Roman Numerals

roman_numerals.go

// Package romannumerals provides methods for manipulating numbers into roman numerals
package romannumerals

import "errors"

type RomanNumeral struct {
	Value  int
	Symbol string
}

// RomanNumerals is the mapping between numbers and their corresponding Roman numerals
var RomanNumerals = []RomanNumeral{
	{1000, "M"},
	{900, "CM"},
	{500, "D"},
	{400, "CD"},
	{100, "C"},
	{90, "XC"},
	{50, "L"},
	{40, "XL"},
	{10, "X"},
	{9, "IX"},
	{5, "V"},
	{4, "IV"},
	{1, "I"},
}

const MINIMUM = 1
const MAXIMUM = 3999

func validateRange(number int) error {
	if number < MINIMUM || number > MAXIMUM {
		return errors.New("number has to be in range [1..3999]")
	}
	return nil
}

func arabicToRoman(number int) string {
	roman := ""
	for _, numeral := range RomanNumerals {
		for number >= numeral.Value {
			number -= numeral.Value
			roman += numeral.Symbol
		}
	}
	return roman
}

// ToRomanNumeral converts an integer to its roman numeral string equivalent
func ToRomanNumeral(number int) (string, error) {
	if err := validateRange(number); err != nil {
		return "", err
	}
	return arabicToRoman(number), nil
}