path: root/2023/info/scheme-after.md

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# Transcript


[[!template new="1" text="""Introduction""" start="00:00:02.120" video="mainVideo-scheme" id="subtitle"]]

[[!template text="""Hello and welcome everyone on EmacsConf 2023.""" start="00:00:02.120" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""I'm Andrew Tropin.""" start="00:00:07.400" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""I work on operating systems and programming languages.""" start="00:00:08.720" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""Today, we discuss Lisps, Schemes, REPLs,""" start="00:00:11.920" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""interactive development,""" start="00:00:16.640" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and how to make your own cozy development environment.""" start="00:00:18.140" video="mainVideo-scheme" id="subtitle"]]

[[!template new="1" text="""Interactive development""" start="00:00:23.280" video="mainVideo-scheme" id="subtitle"]]

[[!template text="""Let's start from interactive development.""" start="00:00:23.280" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""Lisps are famous for a nice""" start="00:00:26.320" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""Interactive Development Experience.""" start="00:00:29.520" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""They have REPLs.""" start="00:00:32.480" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""Emacs Lisp has its own Lisp machine,""" start="00:00:34.000" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and a lot of cool IDE with different functionality""" start="00:00:40.120" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""is already here and providing""" start="00:00:44.720" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""a nice and pleasant experience.""" start="00:00:47.880" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""The question is, is it enough?""" start="00:00:51.620" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""In most cases, yes, but for some languages,""" start="00:00:56.840" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""we have some white spaces, some missing pieces.""" start="00:00:59.921" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""And for example, in Scheme world,""" start="00:01:04.840" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""we already have a few tools.""" start="00:01:08.300" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""We have REPL, we have integration for REPL in Emacs,""" start="00:01:10.880" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""but is it enough?""" start="00:01:14.600" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""Let's see.""" start="00:01:16.680" video="mainVideo-scheme" id="subtitle"]]

[[!template new="1" text="""REPL: Read Eval Print Loop""" start="00:01:18.180" video="mainVideo-scheme" id="subtitle"]]

[[!template text="""We know that Emacs is very good for Lisps and REPL.""" start="00:01:18.180" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""Lisp and Emacs should be a perfect setup.""" start="00:01:22.840" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""But let's see how REPL basically works.""" start="00:01:26.040" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""It's an event loop which does three things.""" start="00:01:30.080" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""It reads an expression, it evaluates the expression,""" start="00:01:34.800" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and it prints the result.""" start="00:01:37.280" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""We can take a simple expression, input it into REPL,""" start="00:01:40.740" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and evaluate it and see the result.""" start="00:01:47.280" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""Very nice, very convenient.""" start="00:01:48.960" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""You can experiment and see immediately what is happening.""" start="00:01:50.820" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""You can even run a long-running process""" start="00:01:55.340" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""which does something.""" start="00:01:57.760" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""You can interrupt it and everything will be okay.""" start="00:01:58.920" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""But the problem appears""" start="00:02:07.200" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""when you start to develop a bigger project.""" start="00:02:08.640" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""And in most cases, you don't do""" start="00:02:11.660" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""your whole development in REPL.""" start="00:02:14.240" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""You do only a small part of it.""" start="00:02:16.400" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""In most cases, you just write""" start="00:02:18.461" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""the source code in text files,""" start="00:02:20.680" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and after that, you run those snippets of code""" start="00:02:22.920" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""from those text files, or run the whole project.""" start="00:02:26.400" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""It's not very convenient to copy and paste""" start="00:02:30.721" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""every time the snippets of code to the REPL,""" start="00:02:33.720" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""see the result, modify the snippet of code,""" start="00:02:36.040" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""copy it again, and so on.""" start="00:02:38.880" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""So people invented some integration""" start="00:02:41.200" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""between REPL and your text editor.""" start="00:02:44.040" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""So you can evaluate expressions inside your text editor""" start="00:02:46.080" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and see the result here.""" start="00:02:51.600" video="mainVideo-scheme" id="subtitle"]]

[[!template new="1" text="""Long-lasting loops""" start="00:02:53.720" video="mainVideo-scheme" id="subtitle"]]

[[!template text="""Works good so far, but what happens""" start="00:02:53.720" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""if we run a long-lasting loop,""" start="00:02:56.680" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""which does a lot of operations.""" start="00:03:02.300" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""As you can see here with a simple example,""" start="00:03:05.000" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""the output of the function,""" start="00:03:07.840" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""stdout of the function is presented here,""" start="00:03:13.600" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and the resulting value is here.""" start="00:03:16.760" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""If you run a long-running process,""" start="00:03:18.800" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""you don't see anything happening.""" start="00:03:22.360" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""And you see there's a watch instead of my cursor.""" start="00:03:24.640" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""Maybe you don't see it, but nothing actually happens,""" start="00:03:29.260" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""at least from the point of view of the user.""" start="00:03:33.720" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""But if we interrupt the evaluation,""" start="00:03:36.380" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""we will see that some process in the background""" start="00:03:38.400" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""was launched, but we didn't see anything.""" start="00:03:41.440" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""Because the REPL is a single-threaded blocking process,""" start="00:03:44.240" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""which reads stdin and prints stdout,""" start="00:03:51.040" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""make the integration""" start="00:03:54.320" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""between the REPL and your text editor""" start="00:03:55.680" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""is not an easy task.""" start="00:03:58.541" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""And even if you do it,""" start="00:04:02.920" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""you have a lot of downsides, usually.""" start="00:04:04.321" video="mainVideo-scheme" id="subtitle"]]

[[!template new="1" text="""Not interruptible""" start="00:04:07.600" video="mainVideo-scheme" id="subtitle"]]

[[!template text="""First of all, the process is not interruptible.""" start="00:04:07.600" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""If you have a remote process which listens on the socket""" start="00:04:13.680" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""to which you connect from your development environment,""" start="00:04:18.480" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and you run some infinite loop, for example,""" start="00:04:21.940" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""you can't interrupt it.""" start="00:04:25.480" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""Because interruption is done via signals,""" start="00:04:28.300" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and signals to remote processes are not usually""" start="00:04:31.240" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""the thing in such integrations.""" start="00:04:35.040" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""Output is also not interactive.""" start="00:04:38.760" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""Usually, for example, here you can see""" start="00:04:41.160" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""when I evaluate the expression,""" start="00:04:45.320" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""the output is captured on the evaluation side,""" start="00:04:47.800" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and after that, after the whole evaluation""" start="00:04:51.120" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""of the whole expression finished,""" start="00:04:53.720" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""I get the result, all the stdout at once.""" start="00:04:56.180" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""And if I run the process which evaluates for 5 seconds,""" start="00:05:06.760" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""I will see the first signs of the life""" start="00:05:09.920" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""only after 5 seconds of evaluation.""" start="00:05:13.781" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""Okay, what else?""" start="00:05:17.040" video="mainVideo-scheme" id="subtitle"]]

[[!template new="1" text="""No protocol""" start="00:05:23.160" video="mainVideo-scheme" id="subtitle"]]

[[!template text="""When you do such integrations, you have no protocol,""" start="00:05:23.160" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""you have just stdin and stdout.""" start="00:05:26.120" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""You print to stdin from your text editor.""" start="00:05:29.760" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""You read from stdout of the process.""" start="00:05:32.920" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""It's hard to tell if evaluation is finished,""" start="00:05:36.680" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""if it requires stdin, and how to extend the REPL""" start="00:05:40.340" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""to make it more featureful, and so on.""" start="00:05:47.320" video="mainVideo-scheme" id="subtitle"]]

[[!template new="1" text="""Not scalable""" start="00:05:51.480" video="mainVideo-scheme" id="subtitle"]]

[[!template text="""And also, such integrations are usually not very scalable.""" start="00:05:51.480" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""For example, if you want to have a completion,""" start="00:05:57.360" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""you type something, you have the completion. Cool.""" start="00:06:14.700" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""But if you run the process and at the same time""" start="00:06:17.461" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""try to have a completion, you don't have it,""" start="00:06:22.040" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""because the evaluation is in progress,""" start="00:06:24.621" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and you can't calculate the completion candidates""" start="00:06:29.800" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""at the same time. To make it more obvious,""" start="00:06:33.280" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""I will start a completion here.""" start="00:06:35.520" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""You see the completion pop-ups.""" start="00:06:41.020" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""I start the evaluation process,""" start="00:06:43.280" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and when I try to complete something,""" start="00:06:46.160" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""the evaluation freezes and there is no completion.""" start="00:06:49.860" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""Not very convenient.""" start="00:06:53.120" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""Usually, you have some long-running processes""" start="00:06:55.480" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and you want them to continue while you have""" start="00:06:58.120" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""your go to definition, completion, and other things.""" start="00:07:01.400" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""Overall, those issues make it quite inconvenient""" start="00:07:08.580" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""to integrate REPL in text editors or development environments,""" start="00:07:13.660" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""so you need something else""" start="00:07:18.420" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""to make the work comfortable.""" start="00:07:21.380" video="mainVideo-scheme" id="subtitle"]]

[[!template new="1" text="""nREPL""" start="00:07:25.860" video="mainVideo-scheme" id="subtitle"]]

[[!template text="""There is already a solution called nREPL.""" start="00:07:25.860" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""It's a synchronous protocol which allows""" start="00:07:28.980" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""to send operations to the server""" start="00:07:31.120" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and receive responses in a synchronous manner.""" start="00:07:34.020" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""And here is a simple example of a few operations.""" start="00:07:37.760" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""First one is cloning the existing session,""" start="00:07:42.160" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and as a response you will get a new session.""" start="00:07:45.080" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""Also you send the evaluation request with code""" start="00:07:49.241" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""that you want to evaluate, and you get two responses.""" start="00:07:52.100" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""First one says that output is captured""" start="00:07:55.640" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and it's equal to &quot;hi\n&quot;,""" start="00:08:00.601" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and after that, you receive an &quot;Evaluation completed&quot;,""" start="00:08:02.840" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""the value of this expression.""" start="00:08:06.561" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""This protocol was developed""" start="00:08:12.440" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""for CIDER development environment.""" start="00:08:14.080" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""It's a Clojure development environment for Emacs.""" start="00:08:15.880" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""It's very cool, featureful, reliable,""" start="00:08:18.760" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and I would say production-ready.""" start="00:08:22.860" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""A lot of professional Clojure developers use it.""" start="00:08:26.900" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""The nREPL protocol is very simple.""" start="00:08:31.500" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""It has a few operations out of the box,""" start="00:08:33.240" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and you can extend it with any arbitrary operation you want.""" start="00:08:38.220" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""I work a lot on Guix codebase and other Scheme projects,""" start="00:08:46.480" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""so the experience I had previously with nREPL""" start="00:08:53.820" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""was not satisfying. I decided""" start="00:08:57.300" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""to just implement nREPL protocol.""" start="00:08:59.400" video="mainVideo-scheme" id="subtitle"]]

[[!template new="1" text="""Arei, Ares, and how to try""" start="00:09:01.740" video="mainVideo-scheme" id="subtitle"]]

[[!template text="""First of all, I implemented nREPL server in Guile.""" start="00:09:01.740" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""I called it `guile-ares-rs`, and used it""" start="00:09:05.720" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""with a generic nREPL client for Emacs.""" start="00:09:11.340" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""It worked.""" start="00:09:13.960" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""It had some rough edges, but overall it was okay.""" start="00:09:14.720" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""And after that, to add more features""" start="00:09:18.640" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""to make the implementation more complete,""" start="00:09:21.640" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""I wrote my own nREPL client for Emacs and called it `arei`.""" start="00:09:25.080" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""And I got almost complete Guile IDE in two months.""" start="00:09:33.220" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""So `ares-rs` is nREPL server implementation.""" start="00:09:40.180" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""`arei` is Emacs client, which uses the same nREPL protocol.""" start="00:09:45.320" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""It utilizes `sesman` package for managing sessions,""" start="00:09:49.680" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""the association of buffers with nREPL connection.""" start="00:09:54.440" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""It has some roots.""" start="00:10:00.080" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""The implementation has some roots""" start="00:10:04.380" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""in Geiser, CIDER, Monroe, and Rail.""" start="00:10:06.640" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""I took small snippets for some parts of functionality.""" start="00:10:09.980" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""I used the CAPF and xref infrastructure""" start="00:10:15.280" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""for completion at point and cross-reference capabilities.""" start="00:10:19.480" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""And by the time of conference, I hope""" start="00:10:23.080" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""that README will be complete enough""" start="00:10:27.680" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""so you will be able to try it yourself.""" start="00:10:30.200" video="mainVideo-scheme" id="subtitle"]]

[[!template new="1" text="""Demo""" start="00:10:34.180" video="mainVideo-scheme" id="subtitle"]]

[[!template text="""Let's see what is possible with it already.""" start="00:10:34.180" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""Let's connect to nREPL server.""" start="00:10:42.680" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""After that, you can evaluate the expression.""" start="00:10:51.900" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""And you see the stdout and the result.""" start="00:10:56.281" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""Very nice, very convenient.""" start="00:11:02.320" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""You have different expression, you evaluate it,""" start="00:11:04.720" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""you get the value of the evaluation.""" start="00:11:08.660" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""You can run an infinite loop""" start="00:11:10.360" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""which prints to stderr and stdout""" start="00:11:12.280" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and you see all necessary stuff.""" start="00:11:15.640" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""Very cool.""" start="00:11:18.600" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""But also, you can interrupt the evaluation,""" start="00:11:19.300" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""which is very convenient if you accidentally""" start="00:11:21.960" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""run an infinite loop.""" start="00:11:25.160" video="mainVideo-scheme" id="subtitle"]]

[[!template new="1" text="""Continuations""" start="00:11:27.640" video="mainVideo-scheme" id="subtitle"]]

[[!template text="""Also, do you remember here we have a few more examples""" start="00:11:27.640" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""that we didn't try yet?""" start="00:11:32.940" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""For example, on usual REPL implementation,""" start="00:11:34.080" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""if I evaluate this expression, I get return value.""" start="00:11:39.160" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""I make a continuation and save it to this variable""" start="00:11:47.600" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and I try to call this evaluation""" start="00:11:50.760" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and I get an exception,""" start="00:11:52.860" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""because the environment in which this continuation""" start="00:11:55.340" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""was created was different and it has redefined""" start="00:11:58.400" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""stdout and stderr to capture it.""" start="00:12:03.480" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""But when I run it one more time,""" start="00:12:06.160" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""when I resume the continuation,""" start="00:12:08.980" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""the environment changed and it doesn't work.""" start="00:12:12.200" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""What happens in `arei`?""" start="00:12:15.800" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""I define continuation, I save the continuation""" start="00:12:17.420" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""for the simple expression""" start="00:12:21.760" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and I resume the continuation with a new argument,""" start="00:12:23.480" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and you can see at the top of the screen""" start="00:12:27.280" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""that it works perfectly fine.""" start="00:12:30.140" video="mainVideo-scheme" id="subtitle"]]

[[!template new="1" text="""Reading from stdin""" start="00:12:32.460" video="mainVideo-scheme" id="subtitle"]]

[[!template text="""Also, with a usual REPL implementation,""" start="00:12:32.460" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""let's see what happens when we have a process""" start="00:12:35.560" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""which reads from stdin.""" start="00:12:40.320" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""I evaluate the expression and nothing visible happens.""" start="00:12:41.920" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""I can try to type `C-g`, `C-c`,""" start="00:12:48.100" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and after some time it will say user interrupt.""" start="00:12:53.000" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""What actually I expect in such a case""" start="00:12:56.560" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""to have a minibuffer which prompts me for the input.""" start="00:13:00.440" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""When I evaluate the same expression in the `arei`,""" start="00:13:04.680" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""you see the prompt at the minibuffer""" start="00:13:10.020" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and here I can tell, &quot;Hello I'm a message from minibuffer&quot;.""" start="00:13:12.200" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""Cool. You will see that this message is printed to stdout,""" start="00:13:21.900" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and unspecified was returned""" start="00:13:26.100" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""as a result of this expression.""" start="00:13:28.680" video="mainVideo-scheme" id="subtitle"]]

[[!template new="1" text="""Fancy example with continuations""" start="00:13:33.420" video="mainVideo-scheme" id="subtitle"]]

[[!template text="""Let's make some fancy example with continuations.""" start="00:13:33.420" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""Continuations is a very cool mechanism""" start="00:13:37.320" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""which is not the topic of today's talk,""" start="00:13:45.080" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""but you can find a lot of interesting information""" start="00:13:48.000" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""in Scheme documentation or in related books,""" start="00:13:51.000" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and I advise you to do it because it's really nice thing""" start="00:13:54.440" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""that is actually applicable""" start="00:13:58.340" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""in many different programming languages.""" start="00:14:00.120" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""Here you can see the infinite loop""" start="00:14:03.520" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""which just prints values increasing one by one.""" start="00:14:05.200" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""And here we save a continuation on each iteration.""" start="00:14:09.160" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""I can call the continuation""" start="00:14:13.300" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and it will resume from the previous saved step.""" start="00:14:18.060" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""And you can see, it resumed from the same step""" start="00:14:21.940" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""we interrupted earlier, but we provided a new value for it.
another value for it.""" start="00:14:27.680" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""We can provide another value""" start="00:14:31.641" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and it resumed from the same spot it was saved earlier.""" start="00:14:33.921" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""But I also can provide a `read-i` value""" start="00:14:39.200" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and if I provide `read-i` value,""" start="00:14:42.580" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""the infinite loop will read the input from stdin""" start="00:14:45.200" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and will continue the evaluation""" start="00:14:50.780" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""with a different `i` provided in this input.""" start="00:14:53.320" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""So let's try to type some arbitrary value""" start="00:14:56.680" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and you see that the loop continued with this value.""" start="00:15:03.040" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""Very nice.""" start="00:15:07.520" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""And every time we could easily interrupt it.""" start="00:15:08.040" video="mainVideo-scheme" id="subtitle"]]

[[!template new="1" text="""Guix API""" start="00:15:13.160" video="mainVideo-scheme" id="subtitle"]]

[[!template text="""Okay, what most annoying thing that I had previously""" start="00:15:13.160" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""with the usual REPL implementation""" start="00:15:17.320" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""that I have a quite nice Guix API""" start="00:15:19.340" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""where I can build packages, systems and other stuff.""" start="00:15:22.760" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""But if I evaluate this expression, I will get an error.""" start="00:15:27.580" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""Okay. I will get an error""" start="00:15:35.360" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""because I don't have an appropriate environment.""" start="00:15:38.040" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""But what I can do, I can connect to the remote REPL""" start="00:15:44.480" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""by creating a server with `guix repl --listen` command""" start="00:15:51.580" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and connecting to it with `geiser-connect` command.""" start="00:15:55.060" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""And now I can evaluate this expression.""" start="00:15:58.620" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""Right?""" start="00:16:01.820" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""Wow.""" start="00:16:03.360" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""Okay.""" start="00:16:10.480" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""It actually doesn't matter for my example.""" start="00:16:14.340" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""I will explain how it doesn't work easily.""" start="00:16:19.040" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""This is a long-running process which prints something""" start="00:16:22.880" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and it can take up to a few minutes.""" start="00:16:26.520" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""And for the whole few minutes I don't see any results,""" start="00:16:29.580" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""the same as with this infinite loop which prints to stdout""" start="00:16:33.360" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""but I don't see anything interactively.""" start="00:16:38.720" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""With `arei`, I can run""" start="00:16:42.200" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""the evaluation of the same expression,""" start="00:16:45.620" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and you will see instantly""" start="00:16:51.440" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""that stdout is presented here in slightly yellowish color.""" start="00:16:54.120" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""I can interrupt the evaluation""" start="00:17:00.201" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""if I don't want to wait until it's finished,""" start="00:17:02.921" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and just after that, I can evaluate another value.""" start="00:17:06.040" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""So that's cool.""" start="00:17:15.780" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""And let's see one more thing.""" start="00:17:23.360" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""We have an infinite loop and we have some completion here.""" start="00:17:25.960" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""And completion still works,""" start="00:17:30.340" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""very nice,""" start="00:17:32.580" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""while the infinite loop is running.""" start="00:17:33.660" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""Okay.""" start="00:17:40.260" video="mainVideo-scheme" id="subtitle"]]

[[!template new="1" text="""Support""" start="00:17:42.060" video="mainVideo-scheme" id="subtitle"]]

[[!template text="""Actually it took me around two months""" start="00:17:42.060" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""of full-time work funded by my own savings,""" start="00:17:44.920" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and you can support and help to the project""" start="00:17:48.040" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""using OpenCollective or by contributing on SourceHut.""" start="00:17:51.600" video="mainVideo-scheme" id="subtitle"]]

[[!template new="1" text="""Future steps - Multiple simultaneous evaluations in different contexts""" start="00:17:57.020" video="mainVideo-scheme" id="subtitle"]]

[[!template text="""The future steps for the project""" start="00:17:57.020" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""include an experimental workflow where you have""" start="00:17:58.700" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""multiple simultaneous evaluation in different contexts.""" start="00:18:03.675" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""For example, you have Fibers, you have Goblins,""" start="00:18:07.540" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""you have some HTTP server or some other thing,""" start="00:18:11.960" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and you want to run all of them independently""" start="00:18:16.920" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""in slightly isolated sessions,""" start="00:18:22.120" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and you want to have the ability""" start="00:18:25.320" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""to still interact with them.""" start="00:18:29.800" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""For example, if they require standard input""" start="00:18:30.960" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""or something else, you want to be able to provide it.""" start="00:18:33.980" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""You want to see the stderr and stdout""" start="00:18:39.240" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""of those long-running processes and so on.""" start="00:18:42.520" video="mainVideo-scheme" id="subtitle"]]

[[!template new="1" text="""Tree-sitter integration""" start="00:18:46.220" video="mainVideo-scheme" id="subtitle"]]

[[!template text="""The second thing is tree-sitter integration""" start="00:18:46.220" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""for better syntax highlighting, code navigation,""" start="00:18:50.240" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and other features.""" start="00:18:53.400" video="mainVideo-scheme" id="subtitle"]]

[[!template new="1" text="""Full-fledged debugger""" start="00:18:56.880" video="mainVideo-scheme" id="subtitle"]]

[[!template text="""And after that, probably we will do a full-fledged debugger""" start="00:18:56.880" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""so you can jump expressions one by one""" start="00:19:01.400" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and see the results and see some intermediate values""" start="00:19:06.240" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""during the evaluation.""" start="00:19:10.780" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""And it's very possible""" start="00:19:13.080" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""because nREPL is a very extensible protocol""" start="00:19:14.480" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and you can implement""" start="00:19:17.080" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""whatever you want on top of it.""" start="00:19:18.200" video="mainVideo-scheme" id="subtitle"]]

[[!template new="1" text="""FAQ - Does it support other Scheme implementations?""" start="00:19:22.760" video="mainVideo-scheme" id="subtitle"]]

[[!template text="""I will answer two probably very frequent questions.""" start="00:19:22.760" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""Does it support other Scheme implementations?""" start="00:19:27.080" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""At the moment, it doesn't,""" start="00:19:30.500" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""but the Scheme implementation is not restricted.""" start="00:19:32.280" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""You have a server which is implemented in your language""" start="00:19:36.520" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and you have a client--in our case, `arei`--""" start="00:19:40.640" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""which communicates with this protocol.""" start="00:19:43.975" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""So if you implement nREPL server in a different language,""" start="00:19:48.320" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""it should work with already implemented `arei` client.""" start="00:19:52.360" video="mainVideo-scheme" id="subtitle"]]

[[!template new="1" text="""Is it possible to use it with other text editors?""" start="00:19:58.380" video="mainVideo-scheme" id="subtitle"]]

[[!template text="""And is it possible to use the same functionality""" start="00:19:58.380" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""in other text editors, for example in VS Code,""" start="00:20:04.080" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""Vim, whatever?""" start="00:20:07.000" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""Yes, it's possible and the case is similar here.""" start="00:20:08.680" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""You have already implemented nREPL server""" start="00:20:13.800" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and you can write your own nREPL client""" start="00:20:16.600" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""in a different text editor and it will work.""" start="00:20:19.360" video="mainVideo-scheme" id="subtitle"]]

[[!template new="1" text="""Conclusion""" start="00:20:22.121" video="mainVideo-scheme" id="subtitle"]]

[[!template text="""I would like to thank the authors and maintainers""" start="00:20:22.121" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and contributors of Guile, Geiser, CIDER, Clojure,""" start="00:20:26.760" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""and Emacs, and all other people""" start="00:20:30.440" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""who are somehow related to the work on those projects""" start="00:20:33.360" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""involved in this talk.""" start="00:20:38.780" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""And I hope the Scheme programming will be enjoyable.""" start="00:20:42.080" video="mainVideo-scheme" id="subtitle"]]

[[!template new="1" text="""Contacts""" start="00:20:45.880" video="mainVideo-scheme" id="subtitle"]]

[[!template text="""If you want to contact me,""" start="00:20:45.880" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""join #tropin IRC channel at libera.chat,""" start="00:20:47.240" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""or drop me a message via email or feediverse""" start="00:20:49.800" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""using `andrew@trop.in` handle.""" start="00:20:53.040" video="mainVideo-scheme" id="subtitle"]]
[[!template text="""I will see you in a bit in Q&A session.""" start="00:20:55.880" video="mainVideo-scheme" id="subtitle"]]



Captioner: sachac

Questions or comments? Please e-mail [emacsconf-org-private@gnu.org](mailto:emacsconf-org-private@gnu.org?subject=Comment%20for%20EmacsConf%202023%20scheme%3A%20Bringing%20joy%20to%20Scheme%20programming)


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