[brandonbloom]

If you watched the video closely, you'll have noticed that this design parameterizes the code by an `io` interface, which enables pluggable implementations. Correctly written code in this style can work transparently with evented or threaded runtimes.

[PaulHoule]

Really? Ordinary synchronous code calls an I/O routine which returns. Asynchronous code calls an I/O routine and then gets called back. That’s a fundamental difference and you can only square it by making the synchronous code look like asynchronous code (callback gets called right away) or asynchronous code look like synchronous code (something like async python which breaks up a subroutine into multiple subroutines and has an event loop manage who calls who.

[int_19h]

OP didn't say that code looks like ordinary sync code, only that it's possible to write code that works equally well for both sync and async. If you RTFA, it looks like this:

  var a = io.async(doWork, .{ io, "hard" });
  ...
  a.await(io);

If your `io` is async, this behaves like an async call returning a promise and then awaiting said promise. If `io` is sync then `io.async` will make the call immediately and `await` is a no-op.