NAME

       Perl::Critic::Policy::Variables::RequireNegativeIndices - Negative array index should be
       used.

AFFILIATION

       This Policy is part of the core Perl::Critic distribution.

DESCRIPTION

       Perl treats a negative array subscript as an offset from the end. Given this, the
       preferred way to get the last element is $x[-1], not $x[$#x] or $x[@x-1], and the
       preferred way to get the next-to-last is $x[-2], not "$x[$#x-1" or $x[@x-2].

       The biggest argument against the non-preferred forms is that their semantics change when
       the computed index becomes negative. If @x contains at least two elements, $x[$#x-1] and
       $x[@x-2] are equivalent to $x[-2]. But if it contains a single element, $x[$#x-1] and
       $x[@x-2] are both equivalent to $x[-1]. Simply put, the preferred form is more likely to
       do what you actually want.

       As Conway points out, the preferred forms also perform better, are more readable, and are
       easier to maintain.

       This policy notices all of the simple forms of the above problem, but does not recognize
       any of these more complex examples:

           $some->[$data_structure]->[$#{$some->[$data_structure]} -1];
           my $ref = \@arr; $ref->[$#arr];

CONFIGURATION

       This Policy is not configurable except for the standard options.

AUTHOR

       Chris Dolan <cdolan@cpan.org>

COPYRIGHT

       Copyright (c) 2006-2011 Chris Dolan.

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

perl v5.24.1                         Perl::Critic::Policy::Variables::RequireNegativeIndices(3pm)