User blog comment:Alemagno12/Divine Presence/@comment-1605058-20170201103530

As described, the U-functions, apart from S, aren't even functions. They don't output anything, they are just some kind of instructions.

Also, what are [1] and [2] in the definition of RO?

In general, if you want to have a well-defined function, it's not a good move to appeal to the reader's imagination ("imagine A is [1]...").