loop

Loop forever with loop and exit with break.

loop

loop repeats forever until explicitly breaked. break can return a value; continue skips the rest of the iteration:

let mut n = 0;
let sonuc = loop {
    n += 1;
    if n % 2 == 0 {
        continue;
    }
    if n > 7 {
        break n * 10;
    }
};
println!("{sonuc}");  // 90

Labeled loops

Labels start with a single quote:

'dis: for i in 1..=3 {
    for j in 1..=3 {
        if i * j == 4 {
            println!("bulundu: {i} x {j}");
            break 'dis;
        }
    }
}

loop is common in retry logic: break on success, otherwise try again.

Exercise First common multiple

Using loop, find the first positive number divisible by both 4 and 6: start with let mut n = 0;, do n += 1 each iteration and return the value with break n once the condition holds. Print the result.

Show example solution

fn main() {
    let mut n = 0;
    let sonuc = loop {
        n += 1;
        if n % 4 == 0 && n % 6 == 0 {
            break n;
        }
    };
    println!("{}", sonuc);
}

Test yourself

What is used to leave the outer loop in nested loops?
- break break;
- Always return
- exit()
- A labeled break: break 'dis;
Show answer

A labeled break: break 'dis; — A loop gets a label written 'name:, and break 'name; ends that loop; continue 'name; works too.

Exit with a value

let ilk = loop {
    n += 7;
    if n % 5 == 0 {
        break ____;
    }
};

Show answer

let ilk = loop {
    n += 7;
    if n % 5 == 0 {
        break n;
    }
};

Statement and effect

loop

Infinite loop
break x

Exits with a value
continue

Next iteration
break 'dis

Leaves the outer loop

Next lesson: while loop

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