40 lines
803 B
Plaintext
40 lines
803 B
Plaintext
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:- object(tracer).
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:- info([
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version is 1.0,
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date is 2004/5/5,
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author is 'Paulo Moura',
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comment is 'A simple tracer meta-interpreter for pure Prolog.']).
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:- public(trace/1).
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:- mode(trace(+goal), zero_or_more).
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:- info(trace/1, [
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comment is 'Traces goal proof.',
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argnames is ['Goal']]).
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trace(Goal) :-
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trace(Goal, 1).
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trace(true, _) :-
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!.
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trace((A, B), Depth) :-
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!, trace(A, Depth), trace(B, Depth).
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trace(A, Depth) :-
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write_trace(call, A, Depth),
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clause(A, B),
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Depth2 is Depth + 1,
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trace(B, Depth2),
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( write_trace(exit, A, Depth)
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;
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write_trace(redo, A, Depth),
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fail).
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trace(A, Depth) :-
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write_trace(fail, A, Depth),
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fail.
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write_trace(Port, Goal, Depth) :-
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write(Depth), write(' '), write(Port), write(': '), writeq(Goal), nl.
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:- end_object.
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