I glanced at the example code and it looked like it allowed side effects, but maybe I was wrong. I haven't had much time to mess with it and seemed to be able to hard crash the repl doing some testing so it's something i'll have to look at later.
Considering how much more approachable this Roc documentation/naming is, I'm wondering if it isn't so that the people writing Wikipedia's math pages are probably the same people that are drawn to and writes Haskell/monad "tutorials".