E-FRP With Priorities
E-FRP is declarative language for programming resource-bounded, event-driven systems. Its original high-level semantics requires that each event handler execute atomically. This facilitates reasoning about E-FRP programs, and therefore is a desirable feature of the language. However, the original compilation strategy requires that each handler complete execution before another event can occur. This implementation treats all events equally; it forces the upper bound on the time needed to respond to any event to be the same. While acceptable for many applications, often some events are more urgent than others We show we can improve the compilation strategy without altering the high-level semantics. Thus, the programmer has more control over responsiveness without taking away the ability to reason about programs at a high level. The programmer controls responsiveness by declaring priorities for events, and the compilation strategy produces code that uses preemption to enforce these priorities. The compilation strategy enjoys the same properties as the original, with the change being that the programmer reasons modulo permutations on the order of event arrivals.