I’m using: SWI-Prolog version 7.6.4 I want the code to: output all solutions. But what I’m getting is: duplicates and wrong solutions My code looks like this: % % 8 friends are sitting at a round table. % seating(Friends) :- length(Friends, 8), member(bruce, Friends), % One o…

Have you tried using trace to step through your code? You are also calling your predicates in different modes. e.g. inbetween with a mixture of grounded and variable terms, do your predicates support being called in that mode? Try testing them out individually with different modes. For example, is…

[image] godmar: I’m particularly confused by the dif/2 predicate Did you get this from somewhere or did you create it yourself? Usually such code is commented in a blog somewhere. FYI if you don’t already know. This is a zebra puzzle and for other ways to solve them including with Prolog …

I know it’s a Zebra puzzle. The Puzzle is a problem from bebraschallenge.org . I wrote the code myself.

With regards to dif/2, I personally think of it as a half way point to constraints and when when I see it being used I ask myself why not just use constraints instead? As such dif/2 is not a friend of mine. The way I currently think of dif/2 is that in true logic any of the statements can be used i…

[image] godmar: (threaded, 64 bits, version 7.6.4) You should consider upgrading to a newer version. :slightly_smiling_face: For Windows and Ubuntu it is relatively easy, I don’t use Mac so can’t speak about that.

[image] godmar: seating(Friends) :- length(Friends, 8), member(bruce, Friends), % One of the friends is Bruce opposite(alice, david, Friends), % Alice is sitting directly opposite of David inbetween(greta, henry, eugene, Friends), % Henry is sitting between Greta a…

So I’ve posted a ‘fixed’ version of your code with as little changes as possible. If you want to figure it out yourself consider the following: With a circular table of 8 seats, any seating position will have 8 solutions by symmetry, so to break symmetry and reduce the number of solutions, put som…

It should be last(Friends, X). Well spotted.

[image] Ian: Hint it isn’t since you are using last incorrectly. I see. It should be last(Friends, X) as per last/2 . The API of this list library isn’t exactly uniform, it seems. member/2 is member(Elem, List). [image] joeblog: Try changing the last two lines to \+ next(franny, alic…

As you may have noticed, Prolog is a bit tribalistic, and using dif (@A, @B) instead of @A \== @B is an example in that since dif is part of Constraint Logic Programming , a dialect as opposed to plain vanilla. Personally, I prefer plain vanilla to dialects since I hop between a lot of programming…

Without using permutation (?Xs, ?Ys) , fixing the argument order in last (?List, ?Last) , and changing the last two lines seating(Friends) :- length(Friends, 8), member(bruce, Friends), % One of the friends is Bruce opposite(alice, david, Friends), % Alice is sitting di…

Find the bug in this logic puzzle

Help!

EricGT November 11, 2021, 4:57pm 6

You should consider upgrading to a newer version. For Windows and Ubuntu it is relatively easy, I don’t use Mac so can’t speak about that.

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Find the bug in this logic puzzle

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