Leafo\ScssPhp\Compiler::libSetNth PHP Method

    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;
    }