Nobody Taught You The Function Philosophy. Let Me Fix That.

I've been writing code for a long time, and the one thing that still separates great developers from average ones isn't the language they use. It's how they think about functions.

Most tutorials give you steps. Nobody talks about the why.
Here is the short version of what I know.

A function is a mini machine with one job. You feed it input, it runs its hidden process, and hands you back a result. That's it. If your function is doing three jobs, you don't have a function. You have chaos with a name.

The argument rule nobody follows: Zero arguments is the ideal. One is clear. Two is acceptable. Three or more? Just trash your function and rethink the design. When arguments pile up, they are telling you something: they want to become a struct or an object.

// Stop doing this 
fn create_user(name: &str, email: &str, age: u32, country: &str) -> User { ... } 
 
// Start doing this 
fn create_user(params: NewUserParams) -> User { ... } 

Single responsibility is not single line. I hear developers repeat this principle like a magic spell and get it completely wrong. One responsibility means one job, not one line of code.

A make_juice function that washes, cuts, and squeezes is still one function. Its job is to make juice. That's fine.

And know when to actually define a function. Not everywhere. Only when you have repetitive code, complex logic that needs a name, or a business concept that deserves to be documented as its own unit.
That's the whole philosophy.

You don't need 10 rules. You need to understand the idea behind the function, and the rules follow naturally.

Check any other sample on how i define function on my original story How to Write a Clean Function

Thats all from my side, hope you enjoy my simple tips and ill bring more tips later Thanks