Show HN: A simple Prolog Interpreter written in a few lines of Python 3

Thanks for the feedback :) I'll definitely check out Datalog - I didn't realize they had logic programming integrated with SQLAlchemy, so it definitely sounds interesting!

Thank you :)

If you want real power for implementing things in as few lines as possible, F# is definitely worth taking a look at as well!

That's so cool! Here is my try in 120 lines of PHP: https://gist.github.com/sanxiyn/3159161

talking about forth, jvtoups elisp forth is a nice one

https://github.com/VincentToups/emacs-utils/blob/master/with...

another blog entry discusses it (scroll down): https://github.com/VincentToups/emacs-utils/blob/master/mona...

still way less lines then I would have thought, especially because it has no dependencies.

Thanks :) Yup, there are also constraint programming libraries in Python which can be used for providing similar functionality, and they're definitely worth checking out!

I've used ad-hoc test case generation using Prolog (MC/DC, all-permutations and other combinatorials) which is a quite natural application for Prolog. Around 2005 I've also used Prolog to generate Java code for analysing/monitoring business processes based on formal business process descriptions on a research project for a Telco who went all-in on SOA. As part of that, I also started to develop decision procedures for static type checking of XML-manipulating programs, along with validators for common markup meta-languages (XSD and subsets). Many years ago I've also developed custom file parsing/business rules checking using Prolog. Plus, a couple ad-hoc parsers and DSLs. And, having developed 2 1/2 prolog engines so far, I'm planning to include ISO Prolog in my upcoming document storage/search system based on SGML, where Prolog is an excellent match since it's both an ISO standard (like SGML), and even has a binding to a document query language based on ISO/IEC 13250 (eg. the proposed "tolog" language, though alternatives were proposed and an ISO/IEC 13250 query language was never completed as a standard).

I wrote a simple date extractor (parsing stuff like "two days ago" from strings) for my hobby website project in prolog [0]. It was great fun to write, and prolog really shines in such applications. And running a prolog microservice in docker feels just a little perverse in a good way. :)

[0] https://github.com/jvnn/date-extractor

I didn't grok anything at first actually. I had familiarity with Prolog and wanted a refresher, so I decided to take a look at implementation attempts done in other languages. I found one which did it in a few lines of Javascript, and you can find the full read and implementation here: https://curiosity-driven.org/prolog-interpreter . My apologies if I didn't make it clear that this is a port of the original write up - I did include this in the first paragraph of the README though, so maybe I should have been clearer?

Originally, I was trying to learn Kotlin along with wanting a refresher in Prolog, so I attempted to do the port using Kotlin and gave up half way though. I didn't have the patience to try to grok too many things at once, so I decided to go with Python due to it's simplicity, popularity, as well as the fact that I'm a lot more fluent in it than I am in Kotlin.

Anyways - sorry if I'm going off track. To answer your question, I grokked the implementation details through porting / refactoring the original code. The concepts / unification I was already familiar with from taking a university course which involved Prolog and from using it in a large AI project. From what I remember, it took me quite a long time to grasp the language and its power!!