NAME

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

DESCRIPTION

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

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

In each case Perl parses this as (!$x), not a negated comparison. Usually if you write this it's a mistake, so the 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 a reasonable way to test for the same (or different) as booleans.

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

LIMITATIONS

User functions called without parentheses are assumed to be usual varargs style, but a prototype can mean that's not true, allowing 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

SEE ALSO

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

HOME PAGE

http://www.geocities.com/user42_kevin/perl-critic-pulp/index.html

COPYRIGHT

Copyright 2008 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.