private static function splitAtValue(array $numbers, $value) : array
{
$lower = [];
$upper = [];
$number_equal = 0;
foreach ($numbers as $number) {
if ($number < $value) {
$lower[] = $number;
} elseif ($number > $value) {
$upper[] = $number;
} else {
$number_equal++;
}
}
return ['lower' => $lower, 'upper' => $upper, 'equal' => $number_equal];
}