I don't know OCaml, but logically it cannot be an actual realized list as the would take up an infinite amount of memory. Whether or not it acts like a function

I don't know OCaml, but logically it cannot be an actual realized list as the would take up an infinite amount of memory. Whether or not it acts like a function in the language wasn't really the point - internally it must still be an iterator unless you have a computer with an infinite amount of memory.