Loops

Rust offers three loop keywords: loop, while, and for. Each suits a different repetition pattern.

loop

loop repeats forever until you break out of it.

fn main() {
    let mut count = 0;
    loop {
        count += 1;
        if count == 3 {
            break;
        }
    }
    println!("{}", count); // 3
}

break with a value

A loop can return a value through break.

fn main() {
    let mut n = 1;
    let result = loop {
        n *= 2;
        if n > 50 {
            break n; // return n from the loop
        }
    };
    println!("{}", result); // 64
}

while

while repeats as long as a condition is true.

fn main() {
    let mut n = 3;
    while n > 0 {
        println!("{}", n);
        n -= 1;
    }
}

for

for iterates over a range or a collection.

fn main() {
    for i in 1..=5 {        // inclusive range 1 to 5
        println!("{}", i);
    }

    let colors = ["red", "green", "blue"];
    for color in colors {
        println!("{}", color);
    }
}

The for loop is the most common and the least error-prone.