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prologboolean-expressiongnu-prolog

Combining two facts via a boolean OR in Gnu Prolog

I'm totally new to Prolog. So please excuse this possibly extermely simple qiuestion: I have a few facts like

likes(peter,cars).
likes(maria,bikes).
likes(walter,bikes).
likes(paul,bikes).
likes(paul,cars).

in a file likes.pl. Now I'm trying to check whether paul likes cars and bikes, so I tried on GNU Prolog's REPL:

| ? - [likes].
| ? - likes(paul,bikes) #\/ likes(paul,cars).

but I get "uncaught exception:...". Obviously I'm doing something wrong. - How can I combine two facts with an AND in GNU Prolog?

Solution

  • The operator you are using #\/ is a Boolean Finite Domain operator used in constraint programming clp(b).

    If you just want a conjunction of two facts A and B, use A, B. If you want a disjunction of them use A; B.

    In your case you can just type likes(paul, bikes), likes(paul, cars)..