Perl::Critic::Policy::ControlStructures::ProhibitNegativeExpressionsInUnlessAndUntilConditions3pm

Don't use operators like "not", "!~", and "le" within "until" and "unless".

Affiliation

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

Overview

    until ($foo ne 'blah') {          #not ok
        ...
    }
    while ($foo eq 'blah') {          #ok
        ...
    }

A number of people have problems figuring out the meaning of doubly negated expressions. "unless" and "until" are both negative constructs, so any negative (e.g. "!~") or reversible operators (e.g. "le") included in their conditional expressions are double negations. Conway considers the following operators to be difficult to understand within "unless" and "until":

  ! not
  !~ ne !=
  <   >   <=  >=  <=>
  lt  gt  le  ge  cmp

Configuration

This Policy is not configurable except for the standard options.

Releases

10 releases since Debian 5.0 (Lenny); the text changed 9 times.

5.0
6.0
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Arch