Cyclomatic complexity

Another possible bottleneck is the cyclomatic complexity of functions. While not directly related to the translation of code from other languages, it's true that Rust can sometimes increase the cyclomatic complexity of the code, since it forces you to check for optional (nullable) results, some complex iterators, functional programming, and so on. This is great for code security, but sometimes the compiler has issues properly optimizing the code we write.

The only way to avoid this is to separate the code into smaller code units that will help the compiler optimize better unit by unit. One way of doing that is by creating smaller functions, with no more than 20–25 branches each. A branch is a place where, depending on one variable, the program will run one code or another. The simplest branch is conditional, an if. There are many others, such as loops (especially when the loop contains returns) or the ? operator. This will create two branches, one for each result option. One of them will return the function while the other will assign the variable.

Nested loops and conditionals make this list grow larger, and the branches can be more and more complex, so you will have to try to divide those deeply nested conditionals in new functions. It's even considered a good practice. As you will see in the Tools section, there are tools that will help you find these bottlenecks.