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    if ( not defined $function_ref ) {
        my $cx = 1;
        my %packages;
    CX:
        while ( my $package = caller $cx ) {

            # Don't retry packages...
            next if exists $packages{$package};
            $packages{$package} = undef;

            # AUTOLOAD using packages are expected to provide a
            # ->can() that works. I don't know if that's a widely
            # known expectation but it's what I'm going to go
            # with. Hash::AsObject gets this wrong.
            if (do {
                    no strict 'refs';    ## no critic NoStrict
                    defined &{"$package\::$function_name"};
                }
                or $package->can($function_name)
                )
            {
                $function_ref = "$package\::$function_name";
                last CX;
            }
        }
        continue {
            ++$cx;
        }
    }

    # We got nuthin! Damn! I'll try for the first AUTOLOAD.
    if ( not defined $function_ref ) {
        my $cx = 1;
        my %packages;
    AUTOLOAD_CX:
        while ( my ($package) = caller $cx ) {
            next if exists $packages{$package};
            $packages{$package} = undef;

            if (do {
                    no strict 'refs';    ## no critic NoStrict
                    defined &{"$package\::AUTOLOAD"};
                }
                or $package->can('AUTOLOAD')
                )
            {
                $function_ref = "$package\::$function_name";
                last AUTOLOAD_CX;
            }
        }
        continue {
            ++$cx;
        }
    }

    if ( not defined $function_ref ) {
	return FAIL;
    }

    # XXX What do to with the first arg?
    my ( undef, $results_ref ) = $term->getarg(1)->to_data;
    my @results = @{ $results_ref->[0] };

    eval {

        no strict 'refs';    ## no critic NoStrict
        $function_ref->(@results);
    };
    if ( my $e = $@ ) {
    
        # Extreme caution here.
        if ( $e =~ UNDEFINED_SUBROUTINE_ERROR ) {
            return FAIL;
        }
    }

    return CONTINUE;
};

sub find { return $PRIMITIVES[ $_[1] ] }

1;

__END__

=head1 NAME

AI::Prolog::Engine::Primitives - The code for running aiprolog builtins

=head1 SYNOPSIS

 my $builtin = AI::Prolog::Engine::Primitives ->find($builtin_id);

=head1 DESCRIPTION

This module contains the code to handle the built-in predicates.  The
L<AI::Prolog::Engine|AI::Prolog::Engine> assigns many builtins an ID
number and this number is used to lookup the sub necessary to execute
the built-in.

=head1 AUTHOR

Curtis "Ovid" Poe, E<lt>moc tod oohay ta eop_divo_sitrucE<gt>

Reverse the name to email me.

=head1 COPYRIGHT AND LICENSE

Copyright 2005 by Curtis "Ovid" Poe

This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.

=cut