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  1.  
  2. % ==========================================
  3. % A. FACTS
  4. % ==========================================
  5.  
  6. parent(robert, john).
  7. parent(roberta, john).
  8. parent(robert, sarah).
  9. parent(roberta, sarah).
  10.  
  11. parent(john, alice).
  12. parent(maria, alice).
  13. parent(john, ben).
  14. parent(maria, ben).
  15.  
  16. parent(sarah, chloe).
  17. parent(david, chloe).
  18.  
  19. % ==========================================
  20. % B. RULES
  21. % ==========================================
  22.  
  23. grandparent(X, Z) :-
  24.     parent(X, Y),
  25.     parent(Y, Z).
  26.  
  27. sibling(X, Y) :-
  28.     parent(P, X),
  29.     parent(P, Y),
  30.     X \= Y.
  31.  
  32. % ==========================================
  33. % C. INPUT AND CHECK RELATIONSHIP
  34. % ==========================================
  35.  
  36. main :-
  37.     read(Relation),
  38.     read(Person1),
  39.     read(Person2),
  40.  
  41.     (   check_relation(Relation, Person1, Person2)
  42.     ->  format('true: ~w(~w, ~w)~n',
  43.                [Relation, Person1, Person2])
  44.     ;   format('false: ~w(~w, ~w)~n',
  45.                [Relation, Person1, Person2])
  46.     ),
  47.     halt.
  48.  
  49. check_relation(parent, X, Y) :-
  50.     parent(X, Y).
  51.  
  52. check_relation(grandparent, X, Y) :-
  53.     grandparent(X, Y).
  54.  
  55. check_relation(sibling, X, Y) :-
  56.     sibling(X, Y).
  57.  
  58. :- initialization(main).
  59.  
Success #stdin #stdout 0.01s 6012KB
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sibling.
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false: sibling(john, roberta)
https://ideone.com/FqMmbd
language:
Prolog (swi 7.6.4)
created:
8 days ago
visibility:
public

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