Marco Russo and Alberto Ferrari’s example goes sideways:
DAX calculation items do not provide full recursion. However, a limited form of recursion is available, known as sideways recursion. We describe this complex topic through examples. Let us start by understanding what recursion is and why it is essential to discuss it. Recursion may occur when a calculation item refers to itself, resulting in an infinite loop within the application of calculation items (read the linked article in case you are not familiar with the concept of “application”, which is different from “execution”). Let us elaborate on this.
Read on for a demonstration of the principle. I haven’t dug into the topic, but I was curious because I’d never heard of “sideways recursion” before. It turns out that there’s some discussion of it in the DAX community and there was something known as Simpson’s sideways recursions from the 1980s, but I’m not sure if that’s the same thing.