File Coverage

blib/lib/PPIx/Regexp/Token/Backtrack.pm

Criterion	Covered	Total	%
statement	25	30	83.3
branch	3	4	75.0
condition			n/a
subroutine	9	10	90.0
pod	5	5	100.0
total	42	49	85.7

=head1 NAME

PPIx::Regexp::Token::Backtrack - Represent backtrack control.

=head1 SYNOPSIS

 use PPIx::Regexp::Dumper;
 PPIx::Regexp::Dumper->new( 'qr{(*ACCEPT)}smx' )
     ->print();

=head1 INHERITANCE

C is a
L.

C has no descendants.

=head1 DESCRIPTION

This class represents one of the backtrack controls.

=head1 METHODS

This class provides no public methods beyond those provided by its
superclass.

=cut

package PPIx::Regexp::Token::Backtrack;

use strict;
use warnings;

use base qw{ PPIx::Regexp::Token };

use PPIx::Regexp::Constant qw{ @CARP_NOT };

our $VERSION = '0.088';

# Return true if the token can be quantified, and false otherwise
sub can_be_quantified { return };

{

    my %explanation = (
	ACCEPT	=> 'Causes match to succeed at the point of the (*ACCEPT)',
	COMMIT	=> 'Causes match failure when backtracked into on failure',
	FAIL	=> 'Always fails, forcing backtrack',
	MARK	=> 'Name branches of alternation, target for (*SKIP)',
	PRUNE	=> 'Prevent backtracking past here on failure',
	SKIP	=> 'Like (*PRUNE) but also discards match to this point',
	THEN	=> 'Force next alternation on failure',
    );

    sub explain {
	my ( $self ) = @_;
	my $verb = $self->verb();
	defined( my $expl = $explanation{$verb} )
	    or return $self->__no_explanation();
	return $expl;
    }

    my %synonym = (
	''	=> 'MARK',
	F	=> 'FAIL',
    );

=head2 arg

This method returns the backtrack control argument specified by the
element. This is the text after the first colon (C<':'>), or the empty
string (C<''>) if none was specified.

=cut

    sub arg {
	my ( $self ) = @_;
	my $content = $self->content();
	$content =~ s/ [^:]* //smx;	# (
	$content =~ s/ \) //smx;
	return $content;
    }

=head2 verb

This method returns the backtrack control verb represented by the
element. This is the text up to but not including the first colon
(C<':'>) if any. If the element specifies C<''> or C<'F">, this method
will return C<'MARK'> or C<'FAIL'>, respectively.

=cut

    sub verb {
	my ( $self ) = @_;
	my $content = $self->content();
	$content =~ s/ \( \* //smx;
	$content =~ s/ [:)] .* //smx;
	defined( my $syn = $synonym{$content} )
	    or return $content;
	return $syn;
    }
}

sub perl_version_introduced {
    return '5.009005';
}

# This must be implemented by tokens which do not recognize themselves.
# The return is a list of list references. Each list reference must
# contain a regular expression that recognizes the token, and optionally
# a reference to a hash to pass to make_token as the class-specific
# arguments. The regular expression MUST be anchored to the beginning of
# the string.
# Note that we have to require a non-lowercase letter after the asterisk
# to avoid grabbing the so-caled alpha_assertions introduced with
# 5.27.9.
# Optimized code ( (*{...}) and (**{...}) ), introduced in 5.37.8, broke
# the non-lowercase requirement. I replaced that with requiring an
# uppercase or a colon (the latter because in (*MARK:foo) you can omit
# the 'MARK').
sub __PPIX_TOKEN__recognize {
    return ( [ qr{ \A \( \* [[:upper:]:] [^\)]* \) }smx ] );
}

# This class gets recognized by PPIx::Regexp::Token::Structure as part
# of its left parenthesis processing.

=begin comment

sub __PPIX_TOKENIZER__regexp {
    my ( $class, $tokenizer, $character ) = @_;

    return $character eq 'x' ? 1 : 0;
}

=end comment

=cut

1;

__END__