[pdimitar]

I don't disagree, but the way Erlang (and thus Elixir) does it is that you get a small stack space to contain your immutable data -- and when you unwind the function the stack just gets thrown away instead of involving the GC which I'd argue is still plenty fast.

I do agree that copying stuff around is generally expensive. I am just unsure how expensive it is in smaller functions that aren't called 10_000 times a second.