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Tackling the Awkward Squad for Reactive Programming: The Actor-Reactor Model

Authors Sam Van den Vonder , Thierry Renaux , Bjarno Oeyen , Joeri De Koster , Wolfgang De Meuter

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Sam Van den Vonder
  • Software Languages Lab, Vrije Universiteit Brussel, Belgium
Thierry Renaux
  • Software Languages Lab, Vrije Universiteit Brussel, Belgium
Bjarno Oeyen
  • Software Languages Lab, Vrije Universiteit Brussel, Belgium
Joeri De Koster
  • Software Languages Lab, Vrije Universiteit Brussel, Belgium
Wolfgang De Meuter
  • Software Languages Lab, Vrije Universiteit Brussel, Belgium

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Sam Van den Vonder, Thierry Renaux, Bjarno Oeyen, Joeri De Koster, and Wolfgang De Meuter. Tackling the Awkward Squad for Reactive Programming: The Actor-Reactor Model. In 34th European Conference on Object-Oriented Programming (ECOOP 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 166, pp. 19:1-19:29, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)


Reactive programming is a programming paradigm whereby programs are internally represented by a dependency graph, which is used to automatically (re)compute parts of a program whenever its input changes. In practice reactive programming can only be used for some parts of an application: a reactive program is usually embedded in an application that is still written in ordinary imperative languages such as JavaScript or Scala. In this paper we investigate this embedding and we distill "the awkward squad for reactive programming" as 3 concerns that are essential for real-world software development, but that do not fit within reactive programming. They are related to long lasting computations, side-effects, and the coordination between imperative and reactive code. To solve these issues we design a new programming model called the Actor-Reactor Model in which programs are split up in a number of actors and reactors. Actors and reactors enforce a strict separation of imperative and reactive code, and they can be composed via a number of composition operators that make use of data streams. We demonstrate the model via our own implementation in a language called Stella.

Subject Classification

ACM Subject Classification
  • Software and its engineering → Data flow languages
  • Software and its engineering → Multiparadigm languages
  • functional reactive programming
  • reactive programming
  • reactive streams
  • actors
  • reactors


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