Also worth noting that the "observing all of time" thing which I mention in the last line suggest that this model of FRP arrows can be acausal (along with other

Also worth noting that the "observing all of time" thing which I mention in the last line suggest that this model of FRP arrows can be acausal (along with other things). Indeed it can! And this is a major semantic and implementation issue. Arrowized FRP does exist and solve these issues, but at the end of the day the ((Time -> a) -> (Time -> b)) model can be considered only inspirational.