FRP in Lean: Stateful combinators, safety, and liveness

Non-pointwise combinators have knowledge of previous timesteps Up to now, every Signal we’ve seen has been stateless. FRP . map and FRP . map2 from last time apply pure functions to the value at each timestep, with no memory of what came before. Real reactive systems have evolving state: the value at time t + 1 depends on the value at time t . In this post, we’ll build up to FRP . accumulate ,…