core.md

ROAP Core

Splitting & Tapping

An async generator can be split or tapped to allow forking the stream of values. These functions asynchronously pull from gen_in and use an ao_fence to emit "rising edge" values. The ao_split(gen_in) function returns a promise for when gen_in is done. The ao_tap(gen_in) function yields the values to create a pass-through generator.

• ao_split().ao_fork() and ao_tap().ao_fork() returns an async iterator of fenced promises.

Note the fork iterators may drop values compared to the source stream. Chaining generators ensures all values are iterated.

Driving Async Generators

To run an async process, ao_run(gen_in) uses an async iterator to pull from gen_in and returns a promise for when gen_in is done.

To drive an async generator, ao_drive(gen_in, gen_out, xform) uses an async iterator to pull from gen_in and push values to gen_out.next.

Deferred Promises

A defer is a Promise that exposes the closure (resolve, reject) parameters as list elements or object attributes.

• ao_defer_o() returns a deferred object {promise, resolve(value) : void, reject(error) : void}

• ao_defer_v() returns a deferred list [promise, resolve(value) : void, reject(error) : void]

• ao_when() and ao_defer_when() creates a when-defined map using ao_defer_v

• ao_when_map(ao_fn_v, db=new Map()) creates a map-like object for deferred defintion registries.

Tracked Fenced Promises

• ao_track(proto) returns a deferred and fenced object {tip() : promise, resume(ans) : void, abort(error) : void, fence() : promise}

• ao_track_v() returns a mutable track list [tip promise, resume(ans) : void, abort(error) : void, fence() : promise]

• ao_track_when() creates a when-defined map using ao_track_v

Misc Utilities

Use ao_iter(iterable) to adapt any iterable (array, DOM element, sync iterator) to an async iterator protocol. Similarly, iter(iterable) adapts any non-async iterable (array, DOM element) to a normal iterator protocol.

(See core/util.jsy for details.)