JoinActors: A Modular Library for Actors with Join Patterns

JoinActors is a Scala 3 library that integrates join patterns — a high-level construct for coordinating concurrent and distributed message-passing components — directly into an existing programming language ecosystem. Unlike prior implementations that required domain-specific languages, JoinActors works as a regular library with a developer-friendly API enabled by Scala 3 metaprogramming. The library features a modular design that allows different matching algorithms to be swapped and compared. This paper details the improved version's architecture, its use of metaprogramming for intuitive pattern-matching syntax, and benchmarks showing significant performance improvements over the original implementation while maintaining fair join pattern matching semantics.