12 lines
238 B
Racket
12 lines
238 B
Racket
#lang datalog
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% Equality test
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ancestor(A, B) :-
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parent(A, B).
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ancestor(A, B) :-
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parent(A, C),
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D = C, % Unification required
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ancestor(D, B).
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parent(john, douglas).
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parent(bob, john).
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parent(ebbon, bob).
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ancestor(A, B)? |