<?php
/**
* Dec2RomanNumConverter
*
* Copyright (C) 2009 Nikola Posa (http://www.nikolaposa.in.rs)
*
* This file is part of Dec2RomanNumConverter.
*
* Dec2RomanNumConverter 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.
*
* Dec2RomanNumConverter 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 Dec2RomanNumConverter. If not, see <http://www.gnu.org/licenses/>.
*/
/**
* Class for converting decimal numbers to Roman numberals and
* vice-versa.
*
* @author Nikola Posa, www.nikolaposa.in.rs
* @license http://opensource.org/licenses/gpl-3.0.html GNU General Public License
*/
class Dec2RomanNumConverter
{
/**
* Common Roman numerals array, with appropriate decimal
* numbers as indexes.
*
* @var array
*/
protected static $_basicNumbers = array
(
1 => 'I',
5 => 'V',
10 => 'X',
50 => 'L',
100 => 'C',
500 => 'D',
1000 => 'M'
);
/**
* Method for converting decimal numbers to Roman numerals.
*
* @param int $decimalNumber
* @return string
*/
public static function dec2roman($decimalNumber)
{
$decimalNumber = (int)$decimalNumber;
//Cheks if argument is larger than 3999 as such numbers
//require a bar above the base numeral.
if ($decimalNumber > 3999) {
require_once 'Dec2RomanNumConverter/Exception.php';
throw new Dec2RomanNumConverter_Exception('Numbers larger than 3999 are not supported.');
}
if (array_key_exists($decimalNumber, self::$_basicNumbers)) {
return self::$_basicNumbers[$decimalNumber];
}
$romanNum = '';
$decNum = (string)$decimalNumber;
$decNumLength = strlen($decNum);
for ($i = 0; $i < $decNumLength; $i++) { //Looping through all numerals.
$currentNumber = (int)$decNum[$i];
if ($currentNumber == 0) {
continue;
}
$decPow = pow(10, ($decNumLength - 1 - $i));
switch ($currentNumber) {
case 4: case 9: //4 and 9 are written using their higher base (5 or 10).
$romanNum .=
self::$_basicNumbers[$decPow]
. self::$_basicNumbers[($currentNumber+1)*$decPow];
break;
case 6: case 7: case 8: //4 and 9 are written using 5 (V) as a base.
$romanNum .=
self::$_basicNumbers[5*$decPow]
. str_repeat(self::$_basicNumbers[$decPow], ($currentNumber-5));
break;
case 5:
$romanNum .= self::$_basicNumbers[5*$decPow];
break;
default:
$romanNum .= str_repeat(self::$_basicNumbers[$decPow], $currentNumber);
break;
}
}
return $romanNum;
}
/**
* Method for converting Roman numerals to decimal numbers.
*
* @param string $romanNumeral
* @return int
*/
public static function roman2dec($romanNumeral)
{
$romanNumeral = trim((string)$romanNumeral);
if (!preg_match('/^[' . implode('', array_values(self::$_basicNumbers)) . ']+$/i', $romanNumeral)) {
require_once 'Dec2RomanNumConverter/Exception.php';
throw new Dec2RomanNumConverter_Exception('Roman numeral "' . $romanNumeral . '" is not valid or it is to large to handle.');
}
$romanNumeral = strtoupper($romanNumeral);
$decNum = 0;
//Early return.
if (($decNum = array_search($romanNumeral, self::$_basicNumbers)) !== false) {
return $decNum;
}
$count = 1;
$basicNumbers = array_flip(self::$_basicNumbers);
for ($i = 0; $i < strlen($romanNumeral); $i++) {
$dn = $basicNumbers[$romanNumeral[$i]];
$nextDn = (isset($romanNumeral[$i+1])) ? $basicNumbers[$romanNumeral[$i+1]] : null;
$decNum += $dn;
if ($nextDn !== null) {
if ($nextDn == $dn) {
$count++;
}
elseif ($nextDn > $dn) { //Special pattern (IV, IX, CM, etc.)?
$temp = $dn * $count; //Value that will be substracted from higher base.
$decNum -= $temp;
$decNum += $nextDn - $temp;
$i++; //Skipping next numeral.
$count = 1;
}
else {
$count = 1;
}
}
}
return $decNum;
}
}
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