44 lines
716 B
Plaintext
44 lines
716 B
Plaintext
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:- object(presort,
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extends(incremental)).
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:- info([
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authors is 'Paulo Moura',
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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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:- uses(quick(_)).
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route(Towns, Route) :-
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arrange(Towns, Towns2),
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^^route(Towns2, Route).
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arrange(Towns, Sorted) :-
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centre(Towns, X, Y),
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quick(geographic(X, Y))::sort(Towns, Sorted).
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centre(Towns, X, Y) :-
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average(Towns, 0, 0, U, V, 0, L),
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X is U/L,
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Y is V/L.
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average([], U, V, U, V, L, L).
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average([Town| Towns], UX, VX, U, V, I, L):-
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Town::at(UT, VT),
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UX2 is UX+UT,
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VX2 is VX+VT,
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I2 is I + 1,
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average(Towns, UX2, VX2, U, V, I2, L).
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:- end_object.
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