swi-mqtt-pack VS anarki

Not a lot of code but a somewhat different use of Prolog than you're likely to see elsewhere. I used my fork of a MQTT library for Prolog (https://github.com/sprior/swi-mqtt-pack) to implement the central controller for my home automation system. The system responds to MQTT events and then coordinates the appropriate action by sending MQTT messages to other home services. Recent versions of SWI-Prolog also support redis and I've started using that to store device configuration and state between services. The MQTT version is actually a reimplementation of my previous version which used CORBA for inter-service communication.

I don't distribute the home automation code however it's pretty specific to my house. The MQTT library provides some building block examples.

I forked an abandoned implementation of MQTT for SWI-Prolog by olsky, my fork is at https://github.com/sprior/swi-mqtt-pack

Look in the examples directory for some basic pub/sub code.

The Prolog code that runs in my house is pretty specific to my house so I figured the best way to open source things would be as a framework more than an implementation. You can contact me via issues on the github repo and prod me into adding some more advanced examples - I've learned a lot since my last commit on the repo.

I've started using the Redis functionality recently added to SWI-Prolog, so my code now responds to MQTT messages and uses state queried from Redis to help determine what actions (implemented by sent MQTT messages) to send out. The beauty is that since I don't do anything that blocks significantly in the Prolog code it is now single threaded - even the MQTT listening. It still responds quickly enough and is MUCH easier to deal with than multi-threaded.

An example of what I'm doing is I built a bunch of ESP8266/EESP32 display devices that control neopixels/OLED/LCD displays. When one of those devices boots it sends a MQTT message announcing its location and capabilities (display type, bit depth, dimensions). Prolog receives that message and then stores that info in Redis. So that device info is all dynamic.

So then later Prolog might get a notification that something is in the driveway. All by MQTT it requests an image from the appropriate camera, then sends the image off to Sighthound and deepstack image recognition servers. The Sighthound front end sends a message back to Prolog with a description of any vehicle spotted which Prolog then matches against known vehicles. If it determines for example that a Fedex truck is in the driveway then Prolog sends notifications around the house - it queries all the display devices from Redis and then based on the capabilities of each devices creates a JSON formatted MQTT message to send to each announcing the Fedex truck. It then also sends a MQTT message to some Java code that connects with Google and sends a push message to an Android app I wrote that displays the alert on my phone and watch.

Before I switched to MQTT I was using Prolog with CORBA as the message transport and back then I also had Visual Basic and MS Agent as part of the system. One night I got bored and a little while later had 3 Peedy the Parrot characters singing Row Your Boat in a round across three different computers coordinated by Prolog. It was actually only a page worth of custom Prolog code for that.

It still is a single single-core server, dang references it frequently when there's unusually high traffic [0]. And the language you're referring to is Arc [1]. They do have caching for not-logged-in users, historically done through nginx [2]. From other comments in this thread, it sounds like they just temporarily put Cloudflare in front of that single server to block a DDoS.

[0] https://news.ycombinator.com/item?id=38310213

[1] https://arclanguage.github.io/

[2] https://news.ycombinator.com/item?id=26473226

Slashdot, reddit, and HN are similar in that the source code was available. For HN, as part of arc under the Artistic license. All 3 abandoned public source code releases.

https://sourceforge.net/projects/slashcode/

https://github.com/arclanguage/anarki

https://github.com/reddit-archive/reddit

>Where is the HN source code right now? Free and Open?

Yes and no.

HN itself is running a proprietary fork of Arc Lisp, which you can find here[0]. The Arc maintainters don't take public PRs or feature requests, and HN itself has numerous changes to the codebase which aren't public for business reasons.

There is a public fork of Arc called Anarki[1] which has no direct connection to HN or Arc Lisp, and for which the community and development is... well... anarchic.

And given the general culture here around minimalism and stasis (not wanting to introduce new features for fear of entropy that would negatively affect the signal to noise ratio and push the site towards Eternal September) chances are it's not likely to happen.

But dang's email is at the bottom of the page if you want to ask him.

[0]http://arclanguage.org/

[1]https://github.com/arclanguage/anarki

The original version was open sourced (Perl artistic License) http://arclanguage.org/ There is an active fork in https://github.com/arclanguage/anarki but it's totally independent and the current conde in HN can be (very) different.

My guess is that it's very difficult to keep all the details of the secret sauce hidden. They change the details very often. For example the front page is ordered by points/time^1.6, but the 1.6 changes from time to time without notice (I think it was 1.8 for some time, perhaps it's 1.8 or something else now. Some people have analyzed the front page and got compatible results, but I don't remember the exponent they found and I'm too lazy to try).

You might find something useful here:

https://github.com/arclanguage/anarki/tree/master/apps/news

It was published in the public version of 2009 https://github.com/arclanguage/anarki/blob/9f2e1dd53b5b66bb4... Look for "contro-factor" (i.e. controversial-factor).

This is old code, and the mods make tweaks here and there without warning, so the details may have changed. (I'm not sure if gravity changed from 1.8 to 1.6 (???).)

I didn't test it personally, but it feels like HN is using something very similar. And there are a few black box analysis of the sorting of the front page that got similar results. Also, minimaxir is the kind of person that is probably running an script to use the HN API to verify the claims.

Absolutely. It's basically the "community version" of Paul Graham's Arc.

Not to mention arc/anarki (hn is/was written in arc - anarki comes with a "news" example app/forum):

https://github.com/arclanguage/anarki/tree/HEAD#readme

arc [1] / racket implimentation of demystifycpp might be able to provide something 'usable' at the command line / straight up web browser html file.

[1] : https://arclanguage.github.io/