Complexity Metrics

And You

"so complicated or intricate as to be hard to understand or deal with"

- dictionary.com

cost of complexity

Complex code is...

Harder to read
Harder to test
Harder to debug

Cheap to produce

Costly to maintain

http://www.trashsociety.com/2010/11/26/the-junk-drawer-trashogram/

Your code has at least one junk drawer

( probably several )

Things aspire to junkiness

Second Law of Thermodynamics (loosely translated)

Lehman's Laws

"[a system] must be continually adapted or it becomes progressively less satisfactory."

"As [a system] evolves its complexity increases unless work is done to maintain or reduce it."

http://en.wikipedia.org/wiki/Lehman's_laws_of_software_evolution

Usage --> Modification --> Complexity

code metaphors

"Technical Debt"

( but no technical interest )

"Code smell"

"Broken Windows"

Bad News

Your code must change

Change increases complexity

"... unless work is done to maintain
or reduce [complexity]."

Multiple Layers

of Defense

Linting
Version control
Automated testing
Code Reviews

http://ariya.ofilabs.com/2012/12/quality-code-via-multiple-layers-of-defense.html

Feedback

Linting = cheap but limited

--------------------------------- the gap -----------------------------------

Testing = cheap-ish but incomplete

Version Control = indirect and incomplete

Code Reviews = super expensive and inconsistent

Metrics

We can use to numbers to track things!

source: http://measuringupblog.com/2013/11/13/are-you-covering-all-of-your-measurement-bases/

This is not dogma, it's engineering.

Halstead Metrics

"The Hydra"

Maurice H. Halstead

1973

Operators

Operands

-->

Given:

r = # of distinct operators

n = # of distinct operands

R = # of total operators

N = # of total operands

then...

everyone is now asleep
http://en.wikipedia.org/wiki/Halstead_complexity_measures

The Chase

Defines measurable properties as formulas
They build on each other to describe relationships
Not all of these measure complexity
Some worth mentioning:
- Volume
- Difficulty
- Effort = Difficulty * Volume
- Estimated Bugs = Volume / 3000