Hello ! I’m using: Prolog 6.2.2 I have a tree : [image] Whith this code : /* The tree database */ :- op(500,xfx,'is_parent'). a is_parent b. c is_parent g. f is_parent l. j is_parent q. a is_parent c. c is_parent h. f is_parent m. j is_parent r. a is_parent d. c i…

Here is some working code :- op(500,xfx,'is_parent'). a is_parent b. c is_parent g. f is_parent l. j is_parent q. a is_parent c. c is_parent h. f is_parent m. j is_parent r. a is_parent d. c is_parent i. h is_parent n. j is_parent s. b is_parent e. d is_parent j…

[image] Mathie: I’m using: Prolog 6.2.2 You really should upgrade. :smiley: Does anyone know how to do that? Of course we do; I take it you would like something more useful. A place that has useful beginner code in many programming languages including Prolog is RosettaCode : Prolog Tasks …

[image] EricGT: level_order_ Thank you for your answer! The problem is that my tree is not a list, which doesn’t really correspond to the example. And I don’t see how to transcribe that with what I’ve done.

[image] Mathie: And I don’t see how to transcribe that with what I’ve done. That was expected. I am looking for something simpler that I can just reference without having to write some code, but so far all of the examples want to use findall/3 which really doesn’t give any insight into how t…

I think that link may predate @jan ’s fix of Swis updating. The current one is https://swish.swi-prolog.org/p/Graphs1.swinb Prolog is “hardwired” to do depthfirst search, whereas doing breadthfirst requires you to manage the frontier list yourself. You invariably also end up having to manage the fro…

[image] EricGT: Also note that this code only works on trees, no DAGs or graphs. The reason being that it does not keep track of which nodes it has visited. That is easily added and would not be surprised if that is one of the next exercises. Thank you very much, you’re really nice! I’ll loo…

If you can get a copy of “The Craft of Prolog” by Richard O’Keefe: in Chapter 2, “Searching”, you will find good explanations of the usual search algorithms (including breadth-first search). There are complete, well explained code listings there. Just go to the library and find the book.

Here’s one way you could do it :- op(500,xfx,'is_parent'). a is_parent b. c is_parent g. f is_parent l. j is_parent q. a is_parent c. c is_parent h. f is_parent m. j is_parent r. a is_parent d. c is_parent i. h is_parent n. j is_parent s. b is_parent e. d is_par…

[image] joeblog: most of us find extremely bewildering at first Not only is is extremely bewildering at first, but bewildering for a long time or until you get someone or something that explains it in a means that makes sense to you. The use of ^ drove me nuts for a long time and I can’t reme…

setof/3 is a great predicate and studying will improve your understanding of Prolog a lot. In many cases though, findall/3 is way easier to understand and a simple sort/2 turns the bag into a set. The moment you discover this is not doing what you want for some particular problem is probably the …

Tree Breadth-First in Prolog

Help!

EricGT November 26, 2019, 8:20pm 5

Still looking for something better but remember that one of the users here did a tutorial on searching.

See: Graph traversal for problem solving tutorial

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Tree Breadth-First in Prolog

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