protected function libSetNth($args)
{
$list = $this->coerceList($args[0]);
$n = $this->assertNumber($args[1]);
if ($n > 0) {
$n--;
} elseif ($n < 0) {
$n += count($list[2]);
}
if (!isset($list[2][$n])) {
$this->throwError('Invalid argument for "n"');
return;
}
$list[2][$n] = $args[2];
return $list;
}