async-package {async}

The async package.

Description

The async package allows you to write sequential-looking code that can pause, return control to R, then pick up where it left off. Async constructs include generators, async/await blocks, and streams (experimental as of async 0.3).

Details

A generator runs until it yields a value and then stops, returning control to R until another value is requested. An async block can pause and return control to R until some data is available, then resume. Generators implement the iteror interface (which is back-compatible with iterator package.) Async blocks implement the promise interface. The new stream construct implements the channel interface, which is defined in this package.

• gen(...) creates a generator (an iterator); within a generator use yield(x) to return a value.

• async(...) creates an async block (a promise); within the async write await(x) to pause on x (another promise).

• stream(...) creates a stream (an asynchronous iterator or channel); in writing a stream you can use both await and yield.)

Theare are some global package options:

async.verbose: (default FALSE) if TRUE, coroutines will print an extremely chatty play-by-play of what they are doing. async.compileLevel: (0) Default compile level for new coroutines. See description of levels under gen. async.paranoid: (FALSE) If true, perform various time-consuming integrity checks on the results of compilation. Meant to be enabled during certain package tests. async.destructive: (TRUE) If true, tear down interpreted coroutines while building compiled replacements. async.sendLater: (TRUE) If true, channels will send messages to listeners in the event loop. If false, messages are sent immediately, which may be faster but may have a higher risk of stack overflow, as well as expose different sorts of bugs in your code.

Author(s)

Peter Meilstrup

See Also

Useful links:

• https://crowding.github.io/async/

• https://github.com/crowding/async/

• Report bugs at https://github.com/crowding/async/issues