cc4531cd1e
git-svn-id: https://yap.svn.sf.net/svnroot/yap/trunk@53 b08c6af1-5177-4d33-ba66-4b1c6b8b522a
60 lines
989 B
Plaintext
60 lines
989 B
Plaintext
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:- object(brick_stack,
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instantiates(constrained_relation)).
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:- info([
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version is 1.0,
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date is 1998/3/23,
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authors is 'Paulo Moura',
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comment is 'Stack of bricks as a constrained binary relation.']).
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descriptor_([top, bottom]).
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domain_(top, brick).
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domain_(bottom, brick).
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key_([top, bottom]).
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cardinality_(top, 0, 1).
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cardinality_(bottom, 0, 1).
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delete_option_(top, cascade).
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delete_option_(bottom, restrict).
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add_tuple([A, B]) :-
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B::position(Xb, Yb),
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Ya2 is Yb + 1,
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{A::move(Xb, Ya2)},
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^^add_tuple([A, B]).
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activ_points_(top, before, []).
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activ_points_(top, after, [move(_, _)]).
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activ_points_(bottom, before, []).
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activ_points_(bottom, after, [move(_, _)]).
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propagate(after, move(X, Y), Top, top, [Top, Bottom]) :-
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!,
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Y2 is Y - 1,
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(Bottom::position(X, Y2) ->
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true
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;
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::remove_tuple([Top, Bottom])).
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propagate(after, move(X, Y), Bottom, bottom, [Top, Bottom]) :-
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!,
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Y2 is Y + 1,
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{Top::move(X, Y2)}.
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:- end_object.
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