How to Redirect within a controller functions with passing id

[eluser]danmontgomery[/eluser]

Code:

function post_list($id) {
    // ...
}

function update_post() {
    $id = $this->input->post('id');

    // ...

    return $this->post_list($id);
    // or
    redirect('controller_name/post_list/'.$id);
}