Prism is like a Lens of Either

My coworker quickly explained one of the more esoteric components (Prism) quite susinctly today:

Prism is a Lens s a where a may or may not be in s. A good example of this is that Prism is like Lens (Either a b) a.

I’m not going to say that this is a hard and fast rule to live by, but I hope it’ll provide a good starting point for some future Lens studies.