<?php
/**
 * Orange Management
 *
 * PHP Version 7.2
 *
 * @package    TBD
 * @copyright  Dennis Eichhorn
 * @license    OMS License 1.0
 * @version    1.0.0
 * @link       http://website.orange-management.de
 */

namespace phpOMS\tests\Math\Functions;

use phpOMS\Math\Functions\Functions;
use phpOMS\Math\Functions\Gamma;

class GammaTest extends \PHPUnit\Framework\TestCase
{
    public function testFactorial()
    {
        self::assertEquals(Functions::fact(4), Gamma::getGammaInteger(5));
    }

    public function testApproximations()
    {
        $stirling = [
            2.15697602, 1.20285073, 0.92213701, 0.83974270, 0.85919025, 0.95950218, 1.14910642, 1.45849038, 1.94540320, 2.70976382,
        ];

        $spouge = [
            2.67893853, 1.35411794, 1.00000000, 0.89297951, 0.90274529, 1.00000000, 1.19063935, 1.50457549, 2.00000000, 2.77815848,
        ];

        $gsl = [
            2.67893853, 1.35411794, 1.00000000, 0.89297951, 0.90274529, 1.00000000, 1.19063935, 1.50457549, 2.00000000, 2.77815848,
        ];

        for ($i = 1; $i <= 10; $i++) {
            self::assertEquals($stirling[$i - 1], Gamma::stirlingApproximation($i / 3), '', 0.01);
            self::assertEquals($spouge[$i - 1], Gamma::spougeApproximation($i / 3), '', 0.01);
            self::assertEquals($gsl[$i - 1], Gamma::lanczosApproximationReal($i / 3), '', 0.01);
        }
    }
}
