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Writing your own BEAM

13 days ago
https://martin.janiczek.cz/2025/11/09/writing-your-own-beam.html
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  • #Elm
  • #BEAM
  • #Concurrency
  • The author explores creating a toy MVP implementation of BEAM, inspired by its process spawning, message passing, and supervision tree features.
  • The implementation uses Elm for its purely functional, single-threaded nature, focusing on the scheduler and main loop without a full language or VM.
  • Continuation Passing Style (CPS) is used for program representation to simplify handling of environments, bindings, and scopes.
  • Key instructions implemented include `End`, `Work`, `Spawn`, `Send`, `Receive`, `Crash`, and `Link`, each contributing to BEAM's concurrency model.
  • A reduction budget is introduced to simulate preemptive scheduling, ensuring fair process execution without actual preemption.
  • Message passing is facilitated through mailboxes, with processes able to selectively receive messages and sleep until relevant messages arrive.
  • Linking processes allows for bidirectional communication of crashes, enabling supervision trees where processes can react to each other's failures.
  • The implementation demonstrates how BEAM's primitives combine to create a robust concurrency model, demystifying its core concepts.
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