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lib/AI/Prolog/Engine/Primitives.pm  view on Meta::CPAN

## no critic (RcsKeywords,PodSections,InterpolationOfMetachars,EmptyQuotes,ConstantPragma,InitializationForLocalVars,LocalVars,PunctuationVars)
package AI::Prolog::Engine::Primitives;
$REVISION = '$Id: Primitives.pm,v 1.1 2005/08/06 23:28:40 ovid Exp $';
$VERSION  = '0.3';
use strict;
use warnings;

use base 'AI::Prolog::Engine';
use Scalar::Util 'looks_like_number';

use aliased 'AI::Prolog::Term';
use aliased 'AI::Prolog::Term::Cut';
use aliased 'AI::Prolog::Term::Number';
use aliased 'AI::Prolog::TermList';
use aliased 'AI::Prolog::TermList::Step';
use aliased 'AI::Prolog::ChoicePoint';

my %DESCRIPTION_FOR;
my $LONGEST_PREDICATE = '';

sub _load_builtins {
    return if keys %DESCRIPTION_FOR;
    require Pod::Simple::Text;
    require Pod::Perldoc;
    my $perldoc     = Pod::Perldoc->new;
    my $builtin_pod = 'AI::Prolog::Builtins';

    my ($found) = $perldoc->grand_search_init( [$builtin_pod] )
        or die "Help failed.  Cannot find documentation for $builtin_pod: $!";
    open my $fh, '<', $found
        or die "Cannot open $found for reading: ($!)";
    my @lines = <$fh>;
    close $fh or die "Cannot close $found: ($!)";

    while (@lines) {
        my $line = shift @lines;
        my $predicate;
        if ( $line =~ /\A=item\s*(\S+)/mx ) {
            $predicate = $1;
            if ( $predicate =~ m{.*/\d+}mx ) {
                my @pod = "=head1 $predicate";
                if ( length $predicate > length $LONGEST_PREDICATE ) {
                    $LONGEST_PREDICATE = $predicate;
                }
                while ( $line = shift @lines ) {
                    if ( $line =~ /\A=(?:item|back)/mx ) {
                        unshift @lines => $line;
                        last;
                    }
                    push @pod => $line;
                }
                push @pod => '=cut';

                # XXX I hate instantiating this here, but there
                # appears to be a bug in parsing if I don't :(
                my $parser = Pod::Simple::Text->new;
                my $output;
                $parser->output_string( \$output );
                $parser->parse_lines( @pod, undef );
                $DESCRIPTION_FOR{$predicate} = $output;
                $output = '';
            }
        }
    }

    return;
}

sub _remove_choices {

    # this implements the cut operator
    my ( $self, $varid ) = @_;
    my @stack;
    my $i = @{ $self->{_stack} };
    while ( $i > $varid ) {
        my $o = pop @{ $self->{_stack} };
        if ( not $o->isa(ChoicePoint) ) {
            push @stack => $o;
        }
        $i--;
    }
    while (@stack) {
        push @{ $self->{_stack} } => pop @stack;
    }

    return;
}

sub _splice_goal_list {
    my ( $self, $term ) = @_;
    my ( $t2, $p, $p1, $ptail );
    my @vars;
    my $i = 0;
    $term = $term->getarg(0);
    while ( $term && $term->getfunctor ne 'null' ) {
        $t2 = $term->getarg(0);
        if ( $t2 eq Term->CUT ) {
            $p = TermList->new( Cut->new( scalar @{ $self->{_stack} } ) );
        }
        else {
            $p = TermList->new($t2);
        }

lib/AI/Prolog/Engine/Primitives.pm  view on Meta::CPAN

    return CONTINUE;
};

$PRIMITIVES[16] = sub {    # gt/2
    my ( $self, $term ) = @_;
    return ( $term->getarg(0)->value > $term->getarg(1)->value )
        ? CONTINUE
        : FAIL;
};

$PRIMITIVES[17] = sub {    # lt/2
    my ( $self, $term ) = @_;
    return ( $term->getarg(0)->value < $term->getarg(1)->value )
        ? CONTINUE
        : FAIL;
};

$PRIMITIVES[19] = sub {    # ge/2
    my ( $self, $term ) = @_;
    return ( $term->getarg(0)->value >= $term->getarg(1)->value )
        ? CONTINUE
        : FAIL;
};

$PRIMITIVES[20] = sub {    # le/2
    my ( $self, $term ) = @_;
    return ( $term->getarg(0)->value <= $term->getarg(1)->value )
        ? CONTINUE
        : FAIL;
};

$PRIMITIVES[22] = sub {    # halt/0
    my ( $self, $term ) = @_;
    $self->halt(1);
    CONTINUE;
};

$PRIMITIVES[23] = sub {    # var/1
    my ( $self, $term, $c ) = @_;
    return $term->getarg(0)->bound() ? FAIL : CONTINUE;
};

# plus(X,Y)  := 25.
# minux(X,Y) := 26.
# mult(X,Y)  := 27.
# div(X,Y)   := 28.
# mod(X,Y)   := 29.

$PRIMITIVES[30] = sub {    # seq/1
    my ( $self, $term, $c ) = @_;
    $self->_splice_goal_list($term);
    CONTINUE;
};

my $HELP_OUTPUT;
$PRIMITIVES[31] = sub {    # help/0
    _load_builtins();
    if ( not $HELP_OUTPUT ) {
        $HELP_OUTPUT = "Help is available for the following builtins:\n\n";
        my @predicates = sort keys %DESCRIPTION_FOR;
        my $length     = length $LONGEST_PREDICATE;
        my $columns    = 5;
        my $format     = join '    ' => ("%-${length}s") x $columns;
        while (@predicates) {
            my @row;
            for ( 1 .. $columns ) {
                push @row => @predicates
                    ? shift @predicates
                    : '';
            }
            $HELP_OUTPUT .= sprintf $format => @row;
            $HELP_OUTPUT .= "\n";
        }
        $HELP_OUTPUT .= "\n";
    }
    AI::Prolog::Engine::_print($HELP_OUTPUT);
    CONTINUE;
};

$PRIMITIVES[32] = sub {    # help/1
    my ( $self, $term, $c ) = @_;
    my $predicate = $term->getarg(0)->to_string;
    _load_builtins();
    if ( my $description = $DESCRIPTION_FOR{$predicate} ) {
        AI::Prolog::Engine::_print($description);
    }
    else {
        AI::Prolog::Engine::_print("No help available for ($predicate)\n\n");
        $PRIMITIVES[31]->();
    }
    CONTINUE;
};

my $gensym_int = 0;
$PRIMITIVES[33] = sub {    # gemsym/1
    my ( $self, $term, $c ) = @_;
    my $t2 = Term->new( 'v' . $gensym_int++, 0 );
    return $t2->unify( $term->getarg(0), $self->{_stack} )
        ? CONTINUE
        : FAIL;
};

use constant UNDEFINED_SUBROUTINE_ERROR => do {
    eval {
        no strict 'refs';    ## no critic NoStrict
        &{'---'};
    };
    my $e = $@;

    # Undefined subroutine &main::--- called at .../Primitives.pm line 12.
    my ($msg) = $e =~ / \A
                        (.+)    # 'Undefined subroutine'
                        (?<=\s) # ' '
                        \S*     # &main::
                        ---/mx
        or die q[Perl's error message changed! Damn! Fix this regex.];

    $msg;
};

$PRIMITIVES[34] = sub {    # perlcall2/2
    my ( $self, $term ) = @_;