NAME¶
Perl::Critic::Policy::Subroutines::ProhibitExcessComplexity - Minimize
complexity by factoring code into smaller subroutines.
AFFILIATION¶
This Policy is part of the core Perl::Critic distribution.
DESCRIPTION¶
All else being equal, complicated code is more error-prone and more expensive to
maintain than simpler code. The first step towards managing complexity is to
establish formal complexity metrics. One such metric is the McCabe score,
which describes the number of possible paths through a subroutine. This Policy
approximates the McCabe score by summing the number of conditional statements
and operators within a subroutine. Research has shown that a McCabe score
higher than 20 is a sign of high-risk, potentially untestable code. See
<
http://en.wikipedia.org/wiki/Cyclomatic_complexity> for some discussion
about the McCabe number and other complexity metrics.
The usual prescription for reducing complexity is to refactor code into smaller
subroutines. Mark Dominus book "Higher Order Perl" also describes
callbacks, recursion, memoization, iterators, and other techniques that help
create simple and extensible Perl code.
CONFIGURATION¶
The maximum acceptable McCabe can be set with the "max_mccabe"
configuration item. Any subroutine with a McCabe score higher than this number
will generate a policy violation. The default is 20. An example section for a
.perlcriticrc:
[Subroutines::ProhibitExcessComplexity]
max_mccabe = 30
NOTES¶
"Everything should be made as simple as possible, but no simpler."
-- Albert Einstein
Complexity is subjective, but formal complexity metrics are still incredibly
valuable. Every problem has an inherent level of complexity, so it is not
necessarily optimal to minimize the McCabe number. So don't get offended if
your code triggers this Policy. Just consider if there
might be a
simpler way to get the job done.
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.