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    }
    my $causes_dict = AI::ExpertSystem::Advanced::Dictionary->new(
            stack => \@facts);
    return $causes_dict;
}

=head2 B<find_rule_by_goal($goal)>

Looks for the first rule that has the given C<goal> in its goals.

If a rule is found then its number is returned, otherwise C<undef> is
returned.

B<NOTE>: Rewrite this method if you are not going to use the C<rules> hash (eg,
you will use a database engine).

=cut
sub find_rule_by_goal {
    my ($self, $goal) = @_;

    my $rule_counter = 0;
    foreach my $rule (@{$self->{'rules'}}) {
        foreach my $rule_goal (@{$rule->{'goals'}}) {
            # Look in id and name for the match
            foreach my $look_in (qw(id name)) {
                if (defined $rule_goal->{$look_in}) {
                    if ($rule_goal->{$look_in} eq $goal) {
                        return $rule_counter;
                    }
                }
            }
        }
        $rule_counter++;
    }
    return undef;
}

=head2 B<get_question($fact)>

Looks for a question about the given C<$fact>. If a question exists then this is
returned, otherwise C<undef> is returned.

B<NOTE>: Rewrite this method if you are not going to use the C<rules> hash (eg,
you will use a database engine).

=cut
sub get_question {
    my ($self, $fact) = @_;

    if (defined $self->{'questions'}->{$fact}) {
        return  $self->{'questions'}->{$fact};
    }
    return undef;
}

=head2 B<get_next_rule($current_rule)>

Returns the ID of the next rule. When there are no more rules to work then
C<undef> should be returned.

When it starts looking for the first rule, C<$current_rule> value will
be C<undef>.

B<NOTE>: Rewrite this method if you are not going to use the C<rules> hash (eg,
you will use a database engine).

=cut
sub get_next_rule {
    my ($self, $current_rule) = @_;

    my $next_rule;
    if (defined $current_rule) {
        $next_rule = $current_rule+1;
    } else {
        $next_rule = 0;
    } 

    if (defined $self->{'rules'}->[$next_rule]) {
        return $next_rule;
    } else {
        return undef;
    }
}

=head1 AUTHOR
 
Pablo Fischer (pablo@pablo.com.mx).

=head1 COPYRIGHT
 
Copyright (C) 2010 by Pablo Fischer.
 
This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.

=cut

1;