How to check if the user is logged in.

[eluser]Cinghius[/eluser]
I have a controller through a login function and various methods to check whether the user can log in, or not. In the end, does a redirect on the home page. I would know, if the user who is logged on the homepage, sees things other than not logged.
To do this, I would have to work on the method $ this-> tank_auth-> is_logged_in ()