Generators and Sequences

Generators in FScript are for pure lazy iteration. They are not the same thing as async streams.

Example: a small sequence

numbers = *(): Sequence<Number> => {
  yield 1
  yield 2
  yield 3
}

Example: derived sequence

countFrom = (start: Number): Sequence<Number> => *() => {
  yield start
  yield start + 1
  yield start + 2
}

Why generators matter

They let you describe ordered lazy values without giving up the rest of the language model:

closures still work
the yielded values are typed
the runtime manages generator state explicitly

Important rule

Draft 0.1 treats generators as pure. Yielding effectful work is a type or effect error.

That means generators are great for:

derived sequences
reusable iteration logic
pure lazy data production

They are not the tool for:

filesystem streaming
network subscriptions
background async workflows

Comparison to JavaScript

The syntax will feel familiar if you know JS generators, but the role is narrower. FScript uses generators for pure lazy sequences and keeps effectful streaming as a separate future abstraction.