NAME¶
Perl::Critic::Policy::Modules::ProhibitExcessMainComplexity - Minimize
complexity in code that is outside of 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 block of code. This
Policy approximates the McCabe score by summing the number of conditional
statements and operators within a block of code. 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.
Whereas Perl::Critic::Policy::Subroutines::ProhibitExcessComplexity scores the
complexity of each subroutine, this Policy scores the total complexity of all
the code that is
outside of any subroutine declaration.
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 score can be set with the "max_mccabe"
configuration item. If the sum of all code
outside any subroutine has a
McCabe score higher than this number, it will generate a Policy violation. The
default is 20. An example section for a
.perlcriticrc:
[Modules::ProhibitExcessMainComplexity]
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.
SEE ALSO¶
Perl::Critic::Policy::Subroutines::ProhibitExcessComplexity
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.