NAME

Array::Iterator::BiDirectional - A subclass of Array::Iterator to allow forwards and backwards iteration

VERSION

This document describes version 0.131 of Array::Iterator::BiDirectional (from Perl distribution Array-Iterator), released on 2021-09-26.

SYNOPSIS

  use Array::Iterator::BiDirectional;

  # create an instance of the iterator
  my $i = Array::Iterator::BiDirectional->new(1 .. 100);

  while ($some_condition_exists) {
      # get the latest item from
      # the iterator
      my $current = $i->get_next();
      # ...
      if ($something_happens) {
          # back up the iterator
          $current = $i->get_previous();
      }
  }

DESCRIPTION

Occasionally it is useful for an iterator to go in both directions, forward and backward. One example would be token processing. When looping though tokens it is sometimes necessary to advance forward looking for a match to a rule. If the match fails, a bi-directional iterator can be moved back so that the next rule can be tried.

METHODS

This is a subclass of Array::Iterator, only those methods that have been added are documented here, refer to the Array::Iterator documentation for more information.

has_previous([$n]): This method works much like "hasNext" does, it will return true (1) unless the beginning of the array has been reached, and false (0) otherwise.
Optional argument has the same meaning except that it specifies $nth previous element.
previous: This method is much like "next". It will return the previous item in the iterator, and throw an exception if it attempts to reach past the beginning of the array.
get_previous: This method is much like "get_next". It will return the previous item in the iterator, and return undef if it attempts to reach past the beginning of the array.
look_back([$n]): This is the counterpart to "peek", it will return the previous items in the iterator, but will not affect the internal counter.
Optional argument has the same meaning except that it specifies $nth previous element.

HOMEPAGE

Please visit the project's homepage at <https://metacpan.org/release/Array-Iterator>.

SOURCE

Source repository is at <https://github.com/perlancar/perl-Array-Iterator>.

AUTHOR

perlancar <perlancar@cpan.org>

ORIGINAL AUTHOR

stevan little, <stevan@iinteractive.com>

CONTRIBUTING

To contribute, you can send patches by email/via RT, or send pull requests on GitHub.

Most of the time, you don't need to build the distribution yourself. You can simply modify the code, then test via:

 % prove -l

If you want to build the distribution (e.g. to try to install it locally on your system), you can install Dist::Zilla, Dist::Zilla::PluginBundle::Author::PERLANCAR, and sometimes one or two other Dist::Zilla plugin and/or Pod::Weaver::Plugin. Any additional steps required beyond that are considered a bug and can be reported to me.

COPYRIGHT AND LICENSE

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

ORIGINAL COPYRIGHT AND LICENSE

<http://www.iinteractive.com>

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

BUGS

Please report any bugs or feature requests on the bugtracker website <https://rt.cpan.org/Public/Dist/Display.html?Name=Array-Iterator>

When submitting a bug or request, please include a test-file or a patch to an existing test-file that illustrates the bug or desired feature.