Hi everyone! I’m Sean, and I think Prolog is really cool. I am helping to make a deductive database and think Prolog is a great tool for the job. I have an unusual requirement, though. I don’t just need to be able to query facts, but also query for the deduction path Prolog took to get to a fact. S…

The problem that your code is trying to solve :slightly_smiling_face:

Sure. If you want full concreteness I can tell you the exact use case of this code. So the database is a collection of objects, properties for each object, and theorems about the properties. Each theorem is a Horn clause. An example theorem (note the real database is not in Prolog—it’s in JSON, but…

This is awesome! I realized this too—the global variables are unnecessary and probably inhibit PL’s ability to reason about the code. Thanks!!

[image] mathmaster13: though it does look like the code is not recursing infinitely, and recursion depth limits do work eventually call_with_depth_limit/3 causes deeper calls to fail. For example: p :- p. p :- write(hello). This loops in Prolog, but not when using a depth limit: ?- call_w…

Hi! Thanks so much for responding. Yes, I ended up using =@=; thank you for the great suggestion! I have another optimization I need to implement, so I don’t have any new news to report. I haven’t implemented trait/6 yet, but I am excited to. However, subsumption seems like it’s very cool and like…

This looks awesome! I’m just a little confused on what I and O are. I think I is a proof, but am more confused about what O is doing.

That’s really neat. I’ll try something like this and let you know how it goes. I’d be curious how to table such a thing, though. For a regular list, I know how to use answer subsumption, but not for a difference list. Also, if anyone likes topology and wants to see what this actually is, check out…

This is running great right now! Thank you to everyone who encouraged tabling. It made a gigantic difference. I still wasn’t able to use a difference list; I used a regular old list that I called “append” with (is that severely less efficient? I bet tabling lessens that impact anyway). But even wit…

Also, I may have found a SWISH bug? It doesn’t happen on the local interpreter: I get no errors there. neg and many other procedures are said to not exist, and yet can be called no problem: neg(A, B). works just fine. The term expansions work too. It all works, but there’s an error nonetheless.

Is there an easy way to view "stack traces" with the interpreter?

General

mathmaster13 March 10, 2026, 6:21am 11

You mean the problem with my code or the problem that my code is trying to solve?

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Is there an easy way to view "stack traces" with the interpreter?

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