I've done few tutorial videos in each TIEA341 course past few years. Most of them have been to clarify some topic on that specific course, but many of them might also be useful in general.
Before watching, note that I have zero production values. I just open my laptop, set it to record and yammer away. I can make two or three unedited videos in an afternoon, but it to edit out all the stammering, stuttering and coding mistakes would probably take days for a single video. I'm too lazy to be bothered about being embarassed in public.
foldland ´foldr` functions work. (If you have trouble computing the foldr example, see this video)