In the language I've been working on for a couple months, Eidos, streams are achieved through iterators as well. It's dead simple. And lazy for loops are iterators, and there is piping syntax. This means you can do this (REPL code):

  >> fn double(iter: $iterator<i32>) {
    return *for x in iter { $yield( x * 2 )}
  }

  >> fn add_ten(iter: $iterator<i32>) {
    return *for x in iter { $yield( x + 10 )}
  }

  >> fn print_all(iter: $iterator<i32>) {
    for x in iter { $print( x )}
  }

  >> const source = *for x in [1, 2, 3] { $yield( x )}

  >> source |> double |> add_ten |> print_all
  12
  14
  16