Scale By The Bay 2019: Tikhon Jelvis, What is Functional Reactive Programming?

ai.bythebay.io Nov 2025, Oakland, full-stack AI conference How can we work with time in functional programming? Traditionally, reactive systems—UIs, web servers, robotic controllers, simulations—are seen as inherently imperative, not suitable for functional programming. This does not have to be the case! Functional Reactive Programming (FRP), lets us have our cake and eat it too: we can use the composable, declarative style we love as functional programmers to write this kind of code. But what is FRP? It's surprisingly hard to get a clear answer without diving deeply into research literature. I will give you an introduction with practical Haskell examples that will get you over the hump to understanding and using FRP. Tikhon Jelvis Target Principal AI Scientist Berkeley Websitejelv.is I picked up Haskell as my first functional language on a whim, and it's stuck with me ever since. I've worked with other functional languages too—a compiler in Racket, a backend service in OCaml—but now I'm back in the Haskell world, working on Target's supply chain optimization team. Apart from programming in Haskell and giving talks, I also actively write about Haskell and programming on Quora and help organize local meetups and events like BayHac