That's one way of doing it, but most formally I think it has to do with whether you're considering the list type in a "data" sense or a "codata" sense. In eithe

That's one way of doing it, but most formally I think it has to do with whether you're considering the list type in a "data" sense or a "codata" sense. In either case you might be talking about the same "shape" of data, but streams are defined under observation as compared to construction.