Execution Model

FScript programs are expression-oriented and async-by-semantics.

The short version

pure expressions evaluate immediately
effectful calls start eagerly when reached
execution suspends only when a not-yet-ready value is consumed
defer delays effect start explicitly

Example

save = (path: String, content: String): String => {
  FileSystem.writeFile(path, content)
  content
}

The runtime starts effectful work as execution reaches it while preserving observable ordering rules.

Why this is unusual

JavaScript exposes most async workflows through Promise, async, and await. FScript moves that concern into the runtime model instead. The goal is direct-looking code with explicit effect semantics.

Design intent

The runtime should preserve observable source ordering unless effects are proven independent.