A generalization. Arrowized FRP (as introduced in Yampa) can be entirely embedded in Elm.

The Automaton library is the beginnings of such an embedding: http://elm-lang.org/docs/Automaton.elm

To be more concrete, in Elm you can work directly with signals if you want. In Yampa you cannot; you only get "signal functions" (which Elm has as well in the form of Automatons).