How to re-implement a cartesian product algorithm

Yes. So did I waste my time, or not? Of course not. I just got a big slap in my programming face. Un pollazo. I over-implemented a cartesian product, without even noticing it. But it's fantastic, I can learn every day :)
I was even showing it around to my friends at work. They didn't notice too! Maybe this algorithm could be used for something else. But I have no fucking clue where :D
Of course I learned a lot, but still, feel a bit stupid. Do not overdo and read more - that is the lesson of today!

Ou programming... my dear...