[scpubgit/DX.git] / lib / DX / Step / Backtrack.pm

package DX::Step::Backtrack;

use DX::Class;

with 'DX::Role::Step';

sub apply_to {
  my ($self, $ss) = @_;
  my ($first_alt, @rest_alt) = @{$ss->alternatives};
  return $ss->but(next_step => $ss->on_exhaustion_step) unless $first_alt;
  trace 'search.backtrack.rewind_to' => $first_alt->[1];
  return $ss->but(
    current_hypothesis => $first_alt->[0],
    alternatives => \@rest_alt,
    next_step => $first_alt->[1],
  );
}

1;
Commit	Line	Data
55131db4	1	package DX::Step::Backtrack;
	2
	3	use DX::Class;
	4
	5	with 'DX::Role::Step';
	6
	7	sub apply_to {
	8	my ($self, $ss) = @_;
	9	my ($first_alt, @rest_alt) = @{$ss->alternatives};
6a0483ff	10	return $ss->but(next_step => $ss->on_exhaustion_step) unless $first_alt;
55131db4	11	trace 'search.backtrack.rewind_to' => $first_alt->[1];
	12	return $ss->but(
	13	current_hypothesis => $first_alt->[0],
	14	alternatives => \@rest_alt,
	15	next_step => $first_alt->[1],
	16	);
	17	}
	18
	19	1;