Practical Principled FRP Forget the past, change the future, FRPNow! Atze van der Ploeg Koen Claessen Chalmers University of Technology, Sweden {atze,koen}@chalmers.se Abstract We present a new interface for practical Functional Reactive Pro- gramming (FRP) that (1) is close in spirit to the original FRP ideas, (2) does not have the original space-leak problems, without using arrows or advanced t