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diff --git a/2022/talks/async.md b/2022/talks/async.md new file mode 100644 index 00000000..5b7fbbc8 --- /dev/null +++ b/2022/talks/async.md @@ -0,0 +1,103 @@ +[[!sidebar content=""]] +[[!meta title="Emacs was async before async was cool"]] +[[!meta copyright="Copyright © 2022 Michael Herstine"]] +[[!inline pages="internal(2022/info/async-nav)" raw="yes"]] + +<!-- Initially generated with emacsconf-generate-talk-page and then left alone for manual editing --> +<!-- You can manually edit this file to update the abstract, add links, etc. ---> + + +# Emacs was async before async was cool +Michael Herstine (IRC: sp1ff) + +[[!inline pages="internal(2022/info/async-before)" raw="yes"]] + +While async is all the rage in the JavaScript, Go and Rust +communities, Emacs has had the ability to (certain) asynchronous +processing all along. I learned this while writing an Emacs package to +program to my music server's API. + +Music Player Daemon is a project that does what it says: hangs out in +the background & plays your music. It has an API that I wanted to call +from Emacs. I had just learned async Rust, so I decided to see if I +could do something similar here. It turns out I could: I wound-up +writing a little async runtime that allows callers to "send" commands +to the daemon by queueing them up and returning immediately. In the +background, as output from previous commands comes in, new commands +are dequeued and sent. + +This required callers to provide callbacks in order to receive the +results of their commands, which led to a situation all too familiar +to Javascript programmers: callback hell. The coda to my story was +(finally) coming to understand Lisp macros in order to extend Emacs +Lisp with a more convenient construct for sending multiple commands. + +This talk will dive into the details of the Emacs Lisp process API, +specifically the Low-Level Network Access API, with illustrations as +to how it can be used to build an asynchronous queue. It will also +introduce Lisp macros and how powerful they can be. + +Michael is a developer and long-time Emacs user from the San Francisco +Bay area. He hacks in C++, Lisp & Rust and thinks a lot about writing +provably correct code. You can find him at: + + - his [home page](https://www.unwoundstack.com) + - on IRC: sp1ff on Libera.Chat + - through [e-mail](mailto:sp1ff@pobox.com) + - or on [Github](https://github.com/sp1ff) + +# Discussion + +- Q: (Referencing the first half of your talk): How does this approach + compare to using tq.el, Emacs' built-in library for transaction + queues? + - A: Great question; should have mentioned that... I took a look, + but chose to just do it "by hand"; I wouldn't have used many + of the features offerred by tq. +- Q: Have you considered using the aio.el library (written by Chris + Wellons) that implements async/await for Emacs lisp using promises? + It's implemented using Elisp's record data structure, and turns + the nested callback structure into regular-looking Elisp code + (without extra keywords etc). +1 + - A: I wasn't aware, but thanks for the pointer-- will + definitely take a look +- Q: not to take away from your excellent work, but are you aware that + EMMS has an MPD client? There's also mpc.el built into Emacs. + - A: Another great point; I am, along with mpdel (another MPD + client for Emacs). They are all full-fledge applications-- I + just wanted a small, tight toolkit +- Q:Have you seen the Lonesome Pine Specials? I saw your music library + and figured you would be interested. My favorite is the one with + Edgar Meyer, Sam Bush, Jerry Douglas, and I think Bela Fleck and + Mark O'Connor? + - A: LOL I haven't, but I I think I will be! +- Q: can you share the code to the macro that creates the callback + tree? + - A: <https://github.com/sp1ff/elmpd/blob/master/elmpd.el#L898> + - thanks! +- Q: would using dynamic/special vars add anything interesting / + easier to async elisp in your opinion? i noticed you using `let` a + lot, but if you defined a variable hmm... not sure if i can :) i + was just wondering if having dynamic binding in Elisp opposed to + something like JS adds some power to async programming + - A: lexical binding is easier to reason about :) +- Q: There's another package (chuntaro?) in addition to wellon's aio + that also implements a coroutine trampoline on the emacs event loop. + any thoughts on the async/await paradigm generally red/blue + functions, etc? + - A: Longer discussion in the chat room, but I think it's a + promising if over-used approach to concurrency. +- Q: How does your project compare to some of the other MPD clients? +- Q: Any thoughts on the async await paradigm generally, red-blue functions, etc.? +- Q: Do you think it's a viable future for Emacs to get out of callback hell? + +Comments from YouTube: + +- Thank you for the informative video Michael! Now I know a way to avoid callback hell in Emacs lisp! +- Nice talk, thank you Michael! + +[[!inline pages="internal(2022/info/async-after)" raw="yes"]] + +[[!inline pages="internal(2022/info/async-nav)" raw="yes"]] + + |