perl::critic::policy::controlstructures::prohibitmutatinglistfun(3) [centos man page]
Perl::Critic::Policy::ControlStructures::ProhibitMutatinUsertContributed)Perl::Critic::Policy::ControlStructures::ProhibitMutatingListFunctions(3) NAME
Perl::Critic::Policy::ControlStructures::ProhibitMutatingListFunctions - Don't modify "$_" in list functions. AFFILIATION
This Policy is part of the core Perl::Critic distribution. DESCRIPTION
"map", "grep" and other list operators are intended to transform arrays into other arrays by applying code to the array elements one by one. For speed, the elements are referenced via a $_ alias rather than copying them. As a consequence, if the code block of the "map" or "grep" modify $_ in any way, then it is actually modifying the source array. This IS technically allowed, but those side effects can be quite surprising, especially when the array being passed is @_ or perhaps "values(%ENV)"! Instead authors should restrict in-place array modification to "for(@array) { ... }" constructs instead, or use "List::MoreUtils::apply()". CONFIGURATION
By default, this policy applies to the following list functions: map grep List::Util qw(first) List::MoreUtils qw(any all none notall true false firstidx first_index lastidx last_index insert_after insert_after_string) This list can be overridden the .perlcriticrc file like this: [ControlStructures::ProhibitMutatingListFunctions] list_funcs = map grep List::Util::first Or, one can just append to the list like so: [ControlStructures::ProhibitMutatingListFunctions] add_list_funcs = Foo::Bar::listmunge LIMITATIONS
This policy deliberately does not apply to "for (@array) { ... }" or "List::MoreUtils::apply()". Currently, the policy only detects explicit external module usage like this: my @out = List::MoreUtils::any {s/^foo//} @in; and not like this: use List::MoreUtils qw(any); my @out = any {s/^foo//} @in; This policy looks only for modifications of $_. Other naughtiness could include modifying $a and $b in "sort" and the like. That's beyond the scope of this policy. SEE ALSO
There is discussion of this policy at <http://perlmonks.org/index.pl?node_id=743445>. AUTHOR
Chris Dolan <cdolan@cpan.org> Michael Wolf <MichaelRWolf@att.net> COPYRIGHT
Copyright (c) 2006-2011 Chris Dolan. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself. perl v5.16.3 2014-Perl::Critic::Policy::ControlStructures::ProhibitMutatingListFunctions(3)
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Perl::Critic::Policy::ControlStructures::ProhibitPostfixUserrContributed PerlPerl::Critic::Policy::ControlStructures::ProhibitPostfixControls(3pm) NAME
Perl::Critic::Policy::ControlStructures::ProhibitPostfixControls - Write "if($condition){ do_something() }" instead of "do_something() if $condition". AFFILIATION
This Policy is part of the core Perl::Critic distribution. DESCRIPTION
Conway discourages using postfix control structures ("if", "for", "unless", "until", "when", "while") because they hide control flow. The "unless" and "until" controls are particularly evil because they lead to double-negatives that are hard to comprehend. The only tolerable usage of a postfix "if"/"when" is when it follows a loop break such as "last", "next", "redo", or "continue". do_something() if $condition; # not ok if ($condition) { do_something() } # ok do_something() while $condition; # not ok while ($condition) { do_something() } # ok do_something() unless $condition; # not ok do_something() unless ! $condition; # really bad if (! $condition) { do_something() } # ok do_something() until $condition; # not ok do_something() until ! $condition; # really bad while (! $condition) { do_something() } # ok do_something($_) for @list; # not ok LOOP: for my $n (0..100) { next if $condition; # ok last LOOP if $other_condition; # also ok next when m< 0 z >xms; # fine too } CONFIGURATION
A set of constructs to be ignored by this policy can specified by giving a value for 'allow' of a string of space-delimited keywords: "if", "for", "unless", "until", "when", and/or "while". An example of specifying allowed flow-control structures in a .perlcriticrc file: [ControlStructures::ProhibitPostfixControls] allow = for if until By default, all postfix control keywords are prohibited. The set of flow-control functions that are exempt from the restriction can also be configured with the 'flowcontrol' directive in your .perlcriticrc file: [ControlStructures::ProhibitPostfixControls] flowcontrol = warn die carp croak cluck confess goto exit This is useful if you're using additional modules that add things like "assert" or "throw". NOTES
The "die", "croak", and "confess" functions are frequently used as flow-controls just like "next" or "last". So this Policy does permit you to use a postfix "if" when the statement begins with one of those functions. It is also pretty common to use "warn", "carp", and "cluck" with a postfix "if", so those are allowed too. The "when" keyword was added to the language after Perl Best Practices was written. This policy treats "when" the same way it does "if", i.e. it's allowed after flow-control constructs. Thanks to brian d foy for the inspiration <http://www.effectiveperlprogramming.com/blog/543>. BUGS
Look for the "do {} while" case and change the explanation to point to page 123 when it is found. RT #37905. AUTHOR
Jeffrey Ryan Thalhammer <jeff@imaginative-software.com> COPYRIGHT
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 v5.14.2 2012-06-0Perl::Critic::Policy::ControlStructures::ProhibitPostfixControls(3pm)