package bytestring

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Efficient, immutable, pattern-matchable, UTF friendly byte strings


Dune Dependency






The Bytestring package implements efficient, immutable, pattern-matchable, UTF friendly byte strings backed up by a rope implementation with mutable iterator instances and a transient interface in the spirit of Clojure transient data.


riot logo

An actor-model multi-core scheduler for OCaml 5.

Quick Start | Tutorial | Reference   

Riot is an actor-model multi-core scheduler for OCaml 5. It brings Erlang-style concurrency to the language, where lightweight processes communicate via message-passing.

open Riot

type Message.t += Hello_world

let () = @@ fun () ->
  let pid =
    spawn (fun () ->
        match receive () with
        | Hello_world ->
   (fun f -> f "hello world from %a!" Pid.pp (self ()));
            shutdown ())
  send pid Hello_world

At its core Riot aims to offer:

  • Automatic multi-core scheduling – when you spawn a new Riot process, it will automatically get allocated on a random scheduler.

  • Lightweight processes – spawn 10 or 10,000 processes as you see fit.

  • Fast, type-safe message passing

  • Selective receive expressions – when receiving messages, you can skim through a process mailbox to consume them in arbitrary order.

  • Process links and monitors to keep track of the lifecycle of processes

Riot also includes:

  • Supervisors to build process hierarchies

  • Logging and Telemetry designed to be multicore friendly

  • an Application interface to orchestrate startup/shutdown of systems

  • Generic Servers for designing encapsulated services like with Elixir's GenServer


At the same time, there's a few things that Riot is not, and does not aim to be.

Primarily, Riot is not a full port of the Erlang VM and it won't support several of its use-cases, like:

  • supporting Erlang or Elixir bytecode

  • hot-code reloading in live applications

  • function-call level tracing in live applications

  • ad-hoc distribution

Quick Start

opam install riot

After that, you can use any of the examples as a base for your app, and run them:

dune exec ./my_app.exe


Riot is the continuation of the work I started with Caramel, an Erlang-backend for the OCaml compiler.

It was heavily inspired by eio by the OCaml Multicore team and miou by Calascibetta Romain and the Robur team, as I learned more about Algebraic Effects. In particular the Proc_state is based on the State module in Miou.

And a thousand thanks to Calascibetta Romain and Antonio Monteiro for the discussions and feedback.

Dependencies (6)

  1. dune >= "3.11"
  2. spices >= "0.0.2"
  3. sedlex >= "3.2"
  4. ppxlib >= "0.31.0"
  5. ocaml >= "5.1.1"
  6. rio = version

Dev Dependencies (2)

  1. odoc with-doc
  2. qcheck with-test & >= "0.21.3"

Used by (3)

  1. gluon
  2. riot >= "0.0.8"
  3. trail




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