Multiple Values with |

Goal of This Episode

Learn to match several possible values in one match arm.

Concept

Sometimes you want several values to run the same code. For instance, Saturday and Sunday are both days off — no need for two separate arms.

Rust uses | (the pipe symbol) to mean “or”:

fn main() {
    let day = 1;
    match day {
        6 | 7 => println!("Day off"),
        _ => println!("Workday"),
    }
}

6 | 7 means “6 or 7.” You can chain as many values as you like with |:

fn main() {
    let n = 3;
    match n {
        1 | 2 | 3 => println!("Top three"),
        _ => println!("Other"),
    }
}

It works with enums too:

enum Color {
    Red,
    Green,
    Blue,
}

fn main() {
    let color = Color::Red;
    match color {
        Color::Red | Color::Blue => println!("Warm or cool color"),
        Color::Green => println!("Green"),
    }
}

Example Code

enum Season {
    Spring,
    Summer,
    Autumn,
    Winter,
}

fn main() {
    // Matching multiple numbers
    let month = 7;

    match month {
        3 | 4 | 5 => println!("Spring"),
        6 | 7 | 8 => println!("Summer"),
        9 | 10 | 11 => println!("Autumn"),
        12 | 1 | 2 => println!("Winter"),
        _ => println!("Invalid month"),
    }

    // Matching multiple enum variants
    let s = Season::Autumn;

    let is_hot = match s {
        Season::Summer => true,
        Season::Spring | Season::Autumn | Season::Winter => false,
    };
    println!("Is the weather hot? {}", is_hot);

    // Combining range patterns with |
    let ch = '5';

    match ch {
        'a'..='z' | 'A'..='Z' => println!("A letter"),
        '0'..='9' => println!("A digit"),
        ' ' | '\t' | '\n' => println!("Whitespace"),
        _ => println!("Other"),
    }
}

Recap

• In match, | means “or,” letting one arm match multiple values.
• Syntax: pattern1 | pattern2 | pattern3 => ....
• Works with enum variants.
• Works with range patterns too: 'a'..='z' | 'A'..='Z'.
• When several values need the same handling, | beats writing multiple arms.