Organizing code into functions

Rust:
Organizing code into functions

How to:

Say you’ve got code that calculates the area of a circle multiple times. Instead of repeating the formula, you wrap it into a function.

fn calculate_circle_area(radius: f64) -> f64 {
    std::f64::consts::PI * radius.powi(2)
}

fn main() {
    let radius = 5.0;
    let area = calculate_circle_area(radius);
    println!("The area of the circle is: {}", area);
}

Output:

The area of the circle is: 78.53981633974483

Deep Dive

Historically, functions come from math, where they map inputs to outputs. In coding, they’ve been around since the assembly days, though we called them ‘subroutines’. Rust functions can return values and even other functions thanks to first-class functions and closures.

Alternatives? Inline code or macros, but they’re messy for complex logic. Objects with methods are another way to organize functionality, a different flavor than standalone functions.

Implementation in Rust is pretty straightforward. Functions declare their parameter types and return type. They’re ‘snake case’ for naming by convention. You’ve got your public functions (pub fn) for use outside the module and private ones for internal use. And Rust has this cool feature where you don’t need a return keyword for the last expression in a function.

Rust:Organizing code into functions

How to:

Deep Dive

See Also

Rust:
Organizing code into functions