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POProlog -- symetrical predicates
 

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    <p>I have to simulate family tree in prolog. And i have problem of symetrical predicates. <strong>Facts:</strong></p> <pre><code>parent(x,y). male(x). female(y). age(x, number). </code></pre> <p><strong>Rules:</strong> </p> <p><code>blood_relation</code> is giving me headache. this is what i have done:</p> <pre><code>blood_relation(X,Y):-ancestor(X,Y). blood_relation(X,Y):-uncle(X,Y);brother(X,Y);sister(X,Y);(mother(Z,Y),sister(X,Z));(father(Z,Y),sister(X,Z));(father(Z,Y),brother(X,Z)). blood_relation(X,Y):-uncle(X,Z),blood_relation(Z,Y). </code></pre> <p>and I am getting i think satisfactory results(i have double prints - can i fix this), problem is that i want that this relation be symmetrical. It is not now. </p> <pre><code>blood_relation(johns_father, joh):yes blood_relation(john,johns_father): no </code></pre> <p>so..is there a way to fix this. And i need query: All pairs that are not in blood_relation..</p> <h2>Update:</h2> <blockquote> <p>What kinds of relationships is the first statement supposed to satisfy? blood_relation(X,Y):-blood_relation(X,Y).</p> </blockquote> <p>sorry..it is a bad copy/paste..it </p> <pre><code>blood_relation(X,Y):-ancestor(X,Y). </code></pre> <p>Now fixed above.</p> <p>here are other rules:</p> <pre><code>father(X,Y):-parent(X,Y),male(X). mother(X,Y):-parent(X,Y),female(X). brother(X,Y):-parent(Z,X),parent(Z,Y),male(X). sister(X,Y):-parent(Z,X),parent(Z,Y),female(X). grandFather(X,Y):-parent(Z,Y),parent(X,Z),male(X). grandMother(X,Y):-parent(Z,Y),parent(X,Z),female(X). uncle(X,Y):-mother(Z,Y),brother(X,Z). ancestor(X,Y):-ancestor(X,Y). ancestor(X,Y):-parent(X,Z),ancestor(Z,Y). </code></pre> <p>Mother's brother is in uncle definition. It's kind of strange. I've got rules that I need to implement, and I don't know how I can implement rules besides that. I'm just confused. </p> <p>Any idea how to make <code>blood_relation</code> symmetric? And <code>not_blood_relation</code> is a new rule. And I need query. This one is really giving me headache. Maybe because relation is written like crap.</p> <p>And there are no more facts. That's all. All rules, and all facts.</p> <p>query.. <code>not(blood_relation(X,Y))</code> doesn't work, and I really don't know why. For example query: </p> <pre><code>age(X,Y), Y&gt;18, not(parent(X,Z)),write(X),nl,fail. </code></pre> <p>works just fine</p>
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