31 lines
452 B
Plaintext
31 lines
452 B
Plaintext
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:- object(city).
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:- public(step/3).
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:- mode(step(+, +, -), zero_or_more).
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:- public(airport/1).
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:- mode(airport(?atom), zero_or_more).
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step(X, Y, P1-P-P2) :-
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\+ same_city(X, Y), !,
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X::airport(XA),
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Y::airport(YA),
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plan(fly)::from(XA, YA, P),
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plan(city)::from(X, XA, P1),
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plan(city)::from(YA, Y, P2).
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step(X, Y, taxi(X, Y)) :-
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same_city(X, Y),
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X \= Y.
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same_city(X, Y) :-
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X::airport(A),
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Y::airport(A).
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:- end_object.
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