2001-06-06 21:07:01 +01:00
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:- object(circular,
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extends(salesman)).
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:- info([
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2003-02-05 00:15:28 +00:00
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author is 'Paulo Moura',
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2001-06-06 21:07:01 +01:00
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version is 1.0,
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date is 2000/4/22,
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comment is '.',
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source is 'Example adopted from the Francis G. McCabe L&O documentation.']).
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:- op(400, yfx, ~).
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route([Town| Towns], Route) :-
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route(Towns, Town~Town, Route).
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route([], Route, Route).
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route([Town| Towns], Route, Route2) :-
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best_place(Route, Town, Best),
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split(Best, Route, Town, Split),
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route(Towns, Split, Route2).
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best_place(Route, Town, Best) :-
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best_place(Route, Town, 10000000, 0, 0, Best).
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best_place(R~T1~T2, Town, XD, _, I, Best) :-
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atom(T1),
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atom(T2),
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extra(T1, Town, T2, XT),
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XT < XD,
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I2 is I + 1,
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best_place(R~T1, Town, XT, I2, I2, Best).
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best_place(R~T1~T2, Town, XD, XI, I, Best) :-
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atom(T1),
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atom(T2),
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I2 is I + 1,
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best_place(R~T1, Town, XD, XI, I2, Best).
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best_place(T1~T2, Town, XD, _, I, Best) :-
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atom(T1),
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atom(T2),
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extra(T1, Town, T2, XT),
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XT < XD,
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Best is I + 1.
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best_place(_~_, _, _, XI, _, XI).
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split(0, Route, Town, Route~Town).
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split(IX, Route~Town1, Town, Split~Town1) :-
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IX2 is IX - 1,
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split(IX2, Route, Town, Split).
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split(1, Route, Town, Town~Route).
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extra(T1, T, T2, E) :-
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T1::crow_flies(T, E1),
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T::crow_flies(T2, E2),
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T1::crow_flies(T2, E3),
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E is E1 + E2 - E3.
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:- end_object.
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