What's wrong with this?



Hi,

I have written a little prog. It tries to find brothers:

father(john,paul).
father(john,simon).

brother(X,Y) :- father(Z,X),father(Z,Y).

But when I ask "Who is the brother of Paul?"

brother(paul,X)

I get the answers "Paul" and "Simon". Prolog says me that Simon is
brother of Paul and additionally Paul is brother of himself.

When I ask "Who is brother of who?" I get a double-weird answer:

brother(X,Y).

Paul-Paul
Paul-Simon
Simon-Simon
Simon-Paul

What's happening? What's wrong is here and how can I avoid this?

Strange thing is this Prolog...

.



Relevant Pages

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