/**
* Axiom: L(n,2) = (n - 1)n! / 2
* Lah number identity when k is 2
*
* @dataProvider dataProivderForLahNumberIdentities
*/
public function testLahNumberIdentityKEqualsTwo(int $n)
{
// Skip exception where n < k
if ($n === 1) {
return;
}
$L⟮n、1⟯ = Combinatorics::lahNumber($n, 2);
$⟮n−1⟯n！／2 = ($n - 1) * Combinatorics::factorial($n) / 2;
$this->assertEquals($L⟮n、1⟯, $⟮n−1⟯n！／2);
}
public function testFactorialBoundsException()
{
$this->setExpectedException('MathPHP\\Exception\\OutOfBoundsException');
Combinatorics::factorial(-1);
}
