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.IX Title "Perl::Critic::Policy::ValuesAndExpressions::NotWithCompare 3pm"
.TH Perl::Critic::Policy::ValuesAndExpressions::NotWithCompare 3pm "2018-05-30" "perl v5.26.2" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
Perl::Critic::Policy::ValuesAndExpressions::NotWithCompare \- logical not used with compare
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This policy is part of the \f(CW\*(C`Perl::Critic::Pulp\*(C'\fR
add-on.  It picks up some cases of logical not \f(CW\*(C`!\*(C'\fR used with a comparison,
like
.PP
.Vb 2
\&    ! $x =~ /^[123]/  # bad
\&    ! $x + $y >= $z   # bad
.Ve
.PP
In each case precedence means Perl parses this as \f(CW\*(C`(!$x)\*(C'\fR, like
.PP
.Vb 2
\&    (! $x) =~ /^[123]/
\&    (! $x) + $y >= $z
.Ve
.PP
rather than a negated comparison.  Usually this is a mistake, so this policy
is under the \*(L"bugs\*(R" theme (see \*(L"\s-1POLICY THEMES\*(R"\s0 in Perl::Critic).
.PP
As a special case, \f(CW\*(C`!\*(C'\fR on both sides of \f(CW\*(C`==\*(C'\fR or \f(CW\*(C`!=\*(C'\fR is allowed,
since it's quite a good way to compare booleans.
.PP
.Vb 2
\&    !$x == !$y   # ok
\&    !$x != !$y   # ok
.Ve
.SH "LIMITATIONS"
.IX Header "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
\&\f(CW\*(C`!\*(C'\fR\-with\-compare expression to go undetected.
.PP
.Vb 3
\&    ! userfunc $x == 123   # indeterminate
\&    # without prototype would be ok:   ! (userfunc ($x==123))
\&    # with ($) prototype would be bad: (! userfunc($x)) == 123
.Ve
.PP
Perl builtins with no args, and constant subs created with \f(CW\*(C`use constant\*(C'\fR
or \f(CW\*(C`sub FOO () {...}\*(C'\fR in the file under test are recognised.  Hopefully
anything else too weird is rare.
.PP
.Vb 1
\&    ! time == 1   # bad
\&
\&    use constant FIVE => 5;
\&    ! FIVE < 1    # bad
\&
\&    sub name () { "foo" }
\&    ! name =~ /bar/    # bad
.Ve
.SH "SEE ALSO"
.IX Header "SEE ALSO"
Perl::Critic::Pulp,
Perl::Critic
.SH "HOME PAGE"
.IX Header "HOME PAGE"
http://user42.tuxfamily.org/perl\-critic\-pulp/index.html
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017 Kevin Ryde
.PP
Perl-Critic-Pulp is free software; you can redistribute it and/or modify it
under the terms of the \s-1GNU\s0 General Public License as published by the Free
Software Foundation; either version 3, or (at your option) any later
version.
.PP
Perl-Critic-Pulp is distributed in the hope that it will be useful, but
\&\s-1WITHOUT ANY WARRANTY\s0; without even the implied warranty of \s-1MERCHANTABILITY\s0
or \s-1FITNESS FOR A PARTICULAR PURPOSE.\s0  See the \s-1GNU\s0 General Public License for
more details.
.PP
You should have received a copy of the \s-1GNU\s0 General Public License along with
Perl-Critic-Pulp.  If not, see <http://www.gnu.org/licenses/>.