When working with functional programming, thinking about "doing" is often the wrong approach, because "doing" is often tied to "change of state". Instead, think about translations/transformations from "what I have" to "what I want".

clickStream.map(f) doesn't "do" anything - it takes a stream, and returns another stream that's the result of f applied to each element of clickStream.

So if I do something like: astream = clickStream.map(a) bstream = clickStream.map(b) cstream = clickStream.map(c)

I've created three streams that are each the result of a particular function applied to the elements of an original stream.