This metric measures the average cyclomatic complexity of the functions in a file.

The cyclomatic complexity of a function is the number of linearly independent execution paths through that function. A path is linearly independent path if it differs from all other paths by at least one node. Straight-line code therefore has a cyclomatic complexity of one, while branches, switches and loops increase cyclomatic complexity.

Functions with a high cyclomatic complexity are typically hard to understand and test. By extension, files whose functions have a high average cyclomatic complexity are problematic, and usually would benefit from refactoring.

As a concrete example, consider the following function:

The control flow graph for this function is as follows:

The graph shows that the number of linearly independent execution paths through the function, and hence its cyclomatic complexity, is 3. The three paths are:

• start -> iEven -> end
• start -> iOdd -> jEven -> end
• start -> iOdd -> jOdd -> end