Structured Event-Driven Concurrency

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Atmos is a programming language that reconciles Structured Concurrency, Event-Driven Programming, and Functional Streams, extending classical structured programming with three main functionalities:

• Structured Deterministic Concurrency:
  • A task primitive with deterministic scheduling provides predictable behavior and safe abortion.
  • Structured primitives compose concurrent tasks with lexical scope (e.g., watching, every, par_or).
  • A tasks container primitive holds attached tasks and control their lifecycle.
  • A pin declaration attaches a task or tasks to its enclosing lexical scope.
• Event Signaling Mechanisms:
  • An await primitive suspends a task and wait for events.
  • An emit primitive signals events and awake awaiting tasks.
• Functional Streams (à la ReactiveX):
  • (experimental)
  • Functional combinators for lazy (infinite) lists.
  • Interoperability with tasks & events: tasks and events as streams, and streams as events.
  • Safe finalization of stateful (task-based) streams.

Atmos is inspired by synchronous programming languages like Céu and Esterel.

Atmos compiles to Lua and relies on lua-atmos for its concurrency runtime.

During 5 seconds, displays Hello World! every second:

require "atmos.env.clock"

watching @5 {
    every @1 {
        print "Hello World!"
    }
}

We first import the builtin clock environment, which provides timers to applications. The program body is a task in Atmos that behaves as follows:

• The watching command will execute its block during 5 seconds.
• The every loop will execute its block every second.
• Once the watching terminates, the body reaches its end, and the program exits cleanly.

sudo luarocks install atmos-lang --lua-version=5.4
atmos <lua-path>/atmos/lang/exs/hello.lua

You may also clone the repository and copy part of the source tree, as follows, into your lua-atmos path (e.g., /usr/local/share/lua/5.4/atmos/):

TODO

The Atmos distribution includes the single-file project argparse.

Atmos depends on lua-atmos.

• Guide
• Manual

An environment is an external component that bridges input events from the real world into an Atmos application.

The standard distribution of Atmos provides the following environments:

• atmos.env.clock A simple pure-Lua environment that uses os.clock to issue timer events.
• atmos.env.socket An environment that relies on luasocket to provide network communication.
• atmos.env.sdl An environment that relies on lua-sdl2 to provide window, mouse, key, and timer events.
• atmos.env.pico An environment that relies on [pico-sdl-lua][pico-sdl-lua] as a simpler alternative do SDL.
• atmos.env.iup An environment that relies on IUP (iup-lua) to provide graphical user interfaces (GUIs).

• A toy problem: Drag, Click, or Cancel
  • click-drag-cancel.atm
• A simple but complete 2D game in Atmos:
  • https://github.com/atmos-lang/sdl-rocks/
• Academic publications (Céu):
  • http://ceu-lang.org/chico/#ceu
• Mailing list (Céu & Atmos):
  • https://groups.google.com/g/ceu-lang