What is actually happening here? How does negating a number result in a negative number less one? I can see that it works, but I'm not sure I understand?

What a fun way to introduce channels (redundant, but fun), this is really cool!

I thought I was being too verbose, turns out everyone just went at it guns blazing...

How would this type of thing be done with a generator ? Sorry for the novice question...

Semi spoiler - but much needed, I just couldn't understand the instructions ... Not sure if they were poorly written, or I'm just silly. Probably the latter ...