Scale By The Bay 2020: Justin Heyes-Jones, Applicative: The Origin Story

ai.bythebay.io Nov 2025, Oakland, full-stack AI conference We've all seen many Monad tutorials, and maybe a few on Functors, but Applicative is lesser known, which is a shame because it has some super powers. In this talk I'll tell the origin story of applicative, and show that once fully understood, it is a very powerful tool in your functional programming toolkit. The talk begins with a quick introduction to pure functional programming with effects, for beginners in the audience. Next we'll look at the original paper in which applicative programming with effects is described. The code will be translated from the original Haskell to Scala, and we can see we can solve problems first with Monads, then more flexibly and elegantly with Applicative. Finally, we'll look at how Applicative plays its part in the much lauded traverse function. Justin Heyes-Jones Yoppworks Software Developer Canada Websitehttps://justinhj.github.io/ Justin started his career making video games and has shipped over 20 titles, working at EA, Activision and Sony amongst others. These days he works at consulting company Yoppworks. He loves to spend time learning more about functional programming, working on open source and sharing his knowledge with others.