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<?php
/**
* webtrees: online genealogy
* Copyright (C) 2026 webtrees development team
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
declare(strict_types=1);
namespace Fisharebest\Webtrees\Services;
use function str_starts_with;
use function strlen;
use function substr;
/**
* Convert to and from Roman Numerals
*/
class RomanNumeralsService
{
// Convert numbers to/from roman numerals
private const array ROMAN_NUMERALS = [
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',
];
/**
* Convert a decimal number to roman numerals
*
* @param int $number
*
* @return string
*/
public function numberToRomanNumerals(int $number): string
{
if ($number < 1) {
// Cannot convert zero/negative numbers
return (string) $number;
}
$roman = '';
foreach (self::ROMAN_NUMERALS as $key => $value) {
while ($number >= $key) {
$roman .= $value;
$number -= $key;
}
}
return $roman;
}
/**
* Convert a roman numeral to decimal
*
* @param string $roman
*
* @return int
*/
public function romanNumeralsToNumber(string $roman): int
{
$num = 0;
foreach (self::ROMAN_NUMERALS as $key => $value) {
while (str_starts_with($roman, $value)) {
$num += $key;
$roman = substr($roman, strlen($value));
}
}
return $num;
}
}
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