In early November 2025, Anthropic had a program giving out $250 credits for Claude Code on the web. It expired on November 18, and on November 15 I still had $220 left.
I was working on something else and as a side effect accidently vibe coded a prolog interpretor on my phone over the weekend.
I haven't used Prolog for 20 years, but it does seem to be roughly correct.
This project is to see how far I can push it. 🚀
Did I really ask Codex to add more Emojis to this README? Yes I did...
> uv run vibeprolog.py ./examples/examples.pl -q "mammal(X)" -v
Loading program from './examples/examples.pl'...
Successfully loaded './examples/examples.pl'
Query: mammal(X).
Solution 1:
X = dog
Solution 2:
X = cat
> uv run vibeprolog.py ./examples/examples.pl -q "grandparent('tom', Y)" -v
Loading program from './examples/examples.pl'...
Successfully loaded './examples/examples.pl'
Query: grandparent('tom', Y).
Solution 1:
Y = ann
Solution 2:
Y = pat
- No human written code. Can prompt things, can tell tools what changes to make but no human written code should be used.
- I don't count config files and docs as code. If it's easier to modify these by hands I will!
- Don't deliberatly add slop. If you notice it doing something wrong, get it fixed.
- Use all the tools you can. Add lots of tests! Add automatic code reviews! Add security audits!
- Don't settle on average code. If an AI is generating slop, tell it what is wrong and how to improve it.
- This is a fun project! Don't take it too seriously.
- I don't know if this works at all. It seems to work, and there are some tests that work but that's it.
- I'm putting it under a MIT license but as AI written code it isn't clear if it can be copyrighted at all
- There are lots of real Prolog implementations that are probably better than this! Use them.
YES!
Please send in your vibe contributions! Just open a PR.
Are you a tool vendor who wants your tools used? Yes! I'd love to use them. I prefer a PR but opening an Issue also works
The libraries in ./library and the examples in ./example are *NOT AI generated!
./library comes from https://github.com/mthom/scryer-prolog/tree/master/src/lib via a git subtree. The files their are licensed as per the headers in those files.
Run the automated suite before pushing changes.
uv run pytest
uv run pytest --run-performance # include long-running performance tests
uv run pytest --run-slow-tests # include tests empirically longer than 4 seconds
--run-performance and --run-slow-tests are opt-in because they pull in heavyweight test cases that would otherwise be skipped.