The Essence & Origins of Functional Reactive Programming • Conal Elliott • YOW! 2015

This presentation was recorded at YOW! 2015. #GOTOcon #YOW https://yowcon.com Conal Elliott - Independent Researcher ABSTRACT Functional Reactive Programming (FRP) is now 20 years old. Although originally motivated by interactive 3D computer graphics, FRP is a general paradigm for describing dynamic (time-varying) information. Such information had traditionally been described in software only indirectly, as successive side effects of sequential execution. In contrast, FRP expressions describe entire evolutions of values over time, representing these evolutions directly as first-class values. From the start, FRP has been based on two simple and fundamental principles, namely (a) having a precise and simple denotation and (b) continuous time. The first property, which Peter Landin called “denotative” (and “genuinely functional”), applies across problem domains and ensures a precise, implementation-independent specification, insulated from operational details as found in efficient implementations. As such, denotative systems can be reasoned about practically and rigorously. The second property (temporal continuity) is domain-specific and is crucial for simple composability, natural specification of behavior via integration and differentiation, and adaptively efficient implementations. Over the last few years, something about FRP has generated a lot of interest among programmers, inspiring several so-called “FRP” systems implemented in various programming languages. Most of these systems, however, lack both of FRP’s fundamental properties. Missing a denotation, they’re defined only in vague and/or operational terms (e.g. “graphs” and “update propagation”). Missing continuous time, they fail to provide temporal modularity (sampling-independence and natural temporal transformability), committing prematurely to sampling rates that may turn out to be too low for accuracy or too high for efficiency. (Discrete notions of imagery have these same drawbacks, remedied by vector graphics and other continuous models.) For the same reason, these systems cannot express behaviors as integrals or derivatives and must instead express explicit approximations, leading to cluttered code with poor quality and/or performance. In this talk, I’ll share with you the essence of the original (denotative and continuous) FRP. You’ll see the thought processes that led to its design, including the care I took to keep the specification both precise and simple, and hopefully, you’ll get a sense of why you might care. As a more in-depth follow-up, the “Denotational Design” workshop explores how to use denotations to design libraries in general. [...] RECOMMENDED BOOKS Eric Normand • Grokking Simplicity • https://amzn.to/3gz7o3C Daniel Higginbotham • Clojure for the Brave and True • https://amzn.to/38tZjsF Ulisses Almeida • Learn Functional Programming with Elixir • https://amzn.to/389grn6 Neal Ford • Functional Thinking • https://amzn.to/3DdP35B Petricek & Skeet • Real-World Functional Programming • https://amzn.to/38diF4M Venkat Subramaniam • Functional Programming in Java • https://amzn.to/2WlOXIt Cristian Salcescu • Functional Programming in JavaScript • https://amzn.to/3y75jBS Richard Feldman • Elm in Action • https://amzn.to/387kujI Jeremy Fairbank • Programming Elm • https://amzn.to/2WhZCE8 Wolfgang Loder • Web Applications with Elm • https://amzn.to/3jblQ3q https://twitter.com/GOTOcon https://www.linkedin.com/company/goto- https://www.facebook.com/GOTOConferences #FRP #FunctionalReactiveProgramming #FunctionalProgramming #ReactiveSystems #SoftwareArchitecture #EventSourcing #ConalElliott #JamesWatson #YOWcon Looking for a unique learning experience? Attend the next GOTO conference near you! Get your ticket at https://gotopia.tech Sign up for updates and specials at https://gotopia.tech/newsletter SUBSCRIBE TO OUR CHANNEL - new videos posted almost daily. https://www.youtube.com/user/GotoConferences/?sub_confirmation=1