Cognitive Complexity

Cognitive Complexity is a measure of how difficult a unit of code is to intuitively understand. Unlike Cyclomatic Complexity, which determines how difficult your code will be to test, Cognitive Complexity tells you how difficult your code will be to read and comprehend.

A method's cognitive complexity is based on a few simple rules:

• Code is not considered more complex when it uses shorthand that the language provides for collapsing multiple statements into one
• Code is considered more complex for each "break in the linear flow of the code"
• Code is considered more complex when "flow breaking structures are nested"

Further reading

• Cognitive Complexity docs
• Cognitive Complexity: A new way of measuring understandability

private methods that are never executed are dead code: unnecessary, inoperative code that should be removed. Cleaning out dead code decreases the size of the maintained codebase, making it easier to understand the program and preventing bugs from being introduced.

Noncompliant Code Example

public class Foo
{
  private function Foo() {}   // Compliant, private empty constructor intentionally used to prevent any direct instantiation of a class.

  public static function doSomething()
  {
    $foo = new Foo();
    ...
  }

  private function unusedPrivateFunction() {  // Noncompliant
  }
}

Compliant Solution

public class Foo
{
  private function Foo(){}   // Compliant, private empty constructor intentionally used to prevent any direct instantiation of a class.

  public static function doSomething()
  {
    $foo = new Foo();
  }
}

See

• CERT, MSC07-CPP. - Detect and remove dead code