Enums Basic

Define enums with data variants and match on them.

Difficulty

Beginner

Code

enum Shape {
    Circle(f64),
    Rectangle(f64, f64),
    Triangle(f64, f64),
}

fn area(shape: &Shape) -> f64 {
    match shape {
        Shape::Circle(r) => std::f64::consts::PI * r * r,
        Shape::Rectangle(w, h) => w * h,
        Shape::Triangle(b, h) => 0.5 * b * h,
    }
}

fn main() {
    let c = Shape::Circle(5.0);
    println!("Area: {:.2}", area(&c));
}

Explanation

Enums define types with multiple variants. Variants can hold data. match must handle all variants.

Key Concepts

• Read the code carefully and understand the data flow
• Try modifying the example to see how it changes behavior
• Run this code in the Rust Playground

Related Topics

Browse more examples in the basics category to build a complete understanding of this topic.