In the Joint Strike Fighter (i.e. F-35) C++ Coding Standards, the limit is 200 lines. But there is also a limit on the cyclomatic complexity number (20 or less)

In the Joint Strike Fighter (i.e. F-35) C++ Coding Standards, the limit is 200 lines. But there is also a limit on the cyclomatic complexity number (20 or less), such that you can either have 200 simples line, or a shorter function that is more complex. You want something that allows you to implement the smallest unit of complexity without having to artificially breaking it down. If you implement a FFT with just 5-line functions, the result is probably going to be more messy than if you did with less restrictive requirements.