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Manual Reference Pages  -  PERL::CRITIC::POLICY::VALUESANDEXPRESSIONS::NOTWITHCOMPARE (3)

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NAME

Perl::Critic::Policy::ValuesAndExpressions::NotWithCompare - logical not used with compare

CONTENTS

DESCRIPTION

This policy is part of the Perl::Critic::Pulp add-on. It picks up some cases of logical not ! used with a comparison, like



    ! $x =~ /^[123]/  # bad
    ! $x + $y >= $z   # bad



In each case precedence means Perl parses this as (!$x), like



    (! $x) =~ /^[123]/
    (! $x) + $y >= $z



rather than a negated comparison. Usually this is a mistake, so this policy is under the bugs theme (see POLICY THEMES in Perl::Critic).

As a special case, ! on both sides of == or != is allowed, since it’s quite a good way to compare booleans.



    !$x == !$y   # ok
    !$x != !$y   # ok



LIMITATIONS

User functions called without parentheses are assumed to be usual varargs style. But a prototype may mean that’s not the case, letting a bad !-with-compare expression to go undetected.



    ! userfunc $x == 123   # indeterminate
    # without prototype would be ok:   ! (userfunc ($x==123))
    # with ($) prototype would be bad: (! userfunc($x)) == 123



Perl builtins with no args, and constant subs created with use constant or sub FOO () {...} in the file under test are recognised. Hopefully anything else too weird is rare.



    ! time == 1   # bad

    use constant FIVE => 5;
    ! FIVE < 1    # bad

    sub name () { "foo" }
    ! name =~ /bar/    # bad



SEE ALSO

Perl::Critic::Pulp, Perl::Critic

HOME PAGE

http://user42.tuxfamily.org/perl-critic-pulp/index.html

COPYRIGHT

Copyright 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015 Kevin Ryde

Perl-Critic-Pulp is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version.

Perl-Critic-Pulp is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with Perl-Critic-Pulp. If not, see <http://www.gnu.org/licenses/>.

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perl v5.20.3 PERL::CRITIC::POLICY::VALUESANDEXPRESSIONS::NOTWITHCOMPARE (3) 2015-01-04

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