Perl::Critic::Policy::InputOutput::ProhibitReadlineInForLoop - Write C<< while( $line = <> ){...} >> instead of C<< for(<>){...} >>.

Perl-Critic documentation Contained in the Perl-Critic distribution.

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NAME

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Perl::Critic::Policy::InputOutput::ProhibitReadlineInForLoop - Write while( $line = <> ){...} instead of for(<>){...}.

AFFILIATION

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

DESCRIPTION

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Using the readline operator in a for or foreach loop is very slow. The iteration list of the loop creates a list context, which causes the readline operator to read the entire input stream before iteration even starts. Instead, just use a while loop, which only reads one line at a time.

  for my $line ( <$file_handle> ){ do_something($line) }      #not ok
  while ( my $line = <$file_handle> ){ do_something($line) }  #ok

CONFIGURATION

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This Policy is not configurable except for the standard options.

AUTHOR

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Jeffrey Ryan Thalhammer <jeff@imaginative-software.com>

COPYRIGHT

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Copyright (c) 2005-2011 Imaginative Software Systems. All rights reserved.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself. The full text of this license can be found in the LICENSE file included with this module.

Perl-Critic documentation Contained in the Perl-Critic distribution. 
##############################################################################
#      $URL: http://perlcritic.tigris.org/svn/perlcritic/trunk/distributions/Perl-Critic/lib/Perl/Critic/Policy/InputOutput/ProhibitReadlineInForLoop.pm $
#     $Date: 2011-05-15 16:34:46 -0500 (Sun, 15 May 2011) $
#   $Author: clonezone $
# $Revision: 4078 $
##############################################################################

package Perl::Critic::Policy::InputOutput::ProhibitReadlineInForLoop;

use 5.006001;
use strict;
use warnings;
use Readonly;

use List::Util qw< first >;

use Perl::Critic::Utils qw{ :severities };
use base 'Perl::Critic::Policy';

our $VERSION = '1.116';

#-----------------------------------------------------------------------------

Readonly::Scalar my $DESC => q{Readline inside "for" loop};
Readonly::Scalar my $EXPL => [ 211 ];

#-----------------------------------------------------------------------------

sub supported_parameters { return ()                             }
sub default_severity     { return $SEVERITY_HIGH                 }
sub default_themes       { return qw< core bugs pbp >            }
sub applies_to           { return qw< PPI::Statement::Compound > }

#-----------------------------------------------------------------------------

sub violates {
    my ( $self, $elem, undef ) = @_;

    return if $elem->type() ne 'foreach';

    my $list = first { $_->isa('PPI::Structure::List') } $elem->schildren()
        or return;

    if (
        my $readline = $list->find_first('PPI::Token::QuoteLike::Readline')
    ) {
        return $self->violation( $DESC, $EXPL, $readline );
    }

    return;  #ok!
}

1;

__END__

#-----------------------------------------------------------------------------


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