The first example of reactive programming in Wikipedia is the ability to define a = b + c, where b and c are changing (and a is changing with them. In Quasar, you can do it imperatively:

  for(;;)
      a.send(b.receive() + c.receive();

Or functionally:

   zip(b, c, (x, y) -> x + y);

RxJava also lets you do the latter. I see that it could also be achieved with a combination of Iteratees and Enumeratees in the code you linked to, using an approach similar to RxJava's, only more complicated and with fewer features.