Functions

Intro

A function is a block of code that usually focuses on a single task. It can take input arguments and return a value of a specific type. Both input arguments and return values are optional.

In Rust, you define a function with the fn keyword, followed by the function name and a set of parentheses. Curly braces contain the function body.

fn pi() -> f32 {
    3.14
}
fn main() {
    let r: f32 = 10.0;
    let pi_value = pi();
    
    println!("Area of cirle: {}", pi_value * r * r);
}

Return

• Implicit Return: Last expression in a block (without a semicolon) is automatically returned.
• Explicit return: Using the return keyword for early returns.

fn fibonacci_series(n: i32) -> i32 {
    // Use `return` keyword to return value.
    if n < 1 { return 0; }
    if n < 2 { return 1; }
    // Last statement of function block without semicolon, return implicitly.
    fibonacci_series(n - 1) + fibonacci_series(n - 2)
}

fn main() {
    let n = 10;
    let result = fibonacci_series(n);
    println!("Fib({}) => {}", n, result);
}