quck question about expr and (( ))

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perl::critic::policy::variables::requirenegativeindices

Perl::Critic::Policy::Variables::RequireNegativeIndices(User Contributed Perl DocumentPerl::Critic::Policy::Variables::RequireNegativeIndices(3pm)

NAME

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

AFFILIATION

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

DESCRIPTION

       Conway points out that

	   $arr[$#arr];
	   $arr[$#arr-1];
	   $arr[@arr-1];
	   $arr[@arr-2];

       are equivalent to

	   $arr[-1];
	   $arr[-2];
	   $arr[-1];
	   $arr[-2];

       and the latter are more readable, performant and maintainable.  The latter is because the programmer no longer needs to keep two variable
       names matched.

       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 v5.14.2							    2012-06-07	      Perl::Critic::Policy::Variables::RequireNegativeIndices(3pm)

Shell Programming and Scripting