Re: [RFC] Fibers

> On Dec 17, 2020, at 4:11 PM, Saif Eddin Gmati <azjezz@protonmail.com> wrote: > > Hello Aaron, > > First, I want to say that I love this proposal and would love to see it land in the next PHP > release, but I have one question regarding this: > > >> Promises result in the “What color is your function” problem as described in the >> introduction of the RFC. Returning promises from functions means that functions calling those >> functions must also return promises, resulting in the entire call stack needing to return promises. > > Hack-Lang provides HH\Asio\join function which allows awaiting > Awaitables in sync code, so you are capable of running multiple async tasks concurrently without > having to declare the entire call stack as "async" or with an "Awaitable" return > type, isn't this possible? > > ``` > use namespace HH\Asio; > > async function async_task(): Awaitable<void> { > await Asio\usleep(1000000); > } > > <<__EntryPoint>> > function main(): void { > $start = microtime(true); > > $async = async { > concurrent { > await async_task(); > await async_task(); > }; > > return 'hello'; > }; > > $result = Asio\join($async); > > printf('Result: %s ( %f )', $result, microtime(true) - $start); // output > "Result: hello ( 1.010382 )" > } > > ``` > > Regards, > > Saif. > Hi Saif, HH\Asio\join() implements a synchronous await (I don't know the details of how its implemented, possibly involving entering and exiting the built-in event loop), but it does not solve the problem that functions using await need to be declared using async and return an Awaitable. Your example declares async_task() as async, while a similar function using the proposed fiber API would not need to change the function declaration to use Fiber::suspend(). There's an example in the RFC using Amp\delay() that is very similar to your code sample. Fibers allow existing interfaces to be implemented using either sync or async I/O because the interface does not need to change to return promises/awaitables. Cheers, Aaron Piotrowski