Rust Basics

Rust Loops: for, while and loop

Three ways to repeat code in Rust, and how break can return a value from loop.

Beginner
3 min read
1 runnable example

What you'll learn

for over a range
while with a condition
loop with break

Run code →

for n in 1..=3

1print

2print

3print

4not in range

The range 1..=3 produces 1, 2 and 3.

Three loops for three jobs

Rust has three loops. for visits each item of a range or collection, while repeats as long as a condition is true, and loop repeats until you break out of it.

1..=3 is a range that includes 3; 1..3 would stop at 2. The while loop ends when countdown reaches 0. break total leaves the loop and returns a value, which is stored in result.

Key points

1..=3 includes 3; 1..3 stops at 2.
while repeats as long as the condition is true.
break value leaves loop and returns the value.

Runnable Rust example

Rust

Run code →

main.rs

fn main() {
    for n in 1..=3 {
        println!("for: {n}");
    }

    let mut countdown = 3;
    while countdown > 0 {
        println!("while: {countdown}");
        countdown -= 1;
    }

    let mut total = 0;
    let result = loop {
        total += 10;
        if total >= 30 {
            break total;
        }
    };
    println!("loop result: {result}");
}

Get a Run button for this example Result of running the code

for: 1
for: 2
for: 3
while: 3
while: 2
while: 1
loop result: 30

Practice

Open the example in the online compiler, change a value or add a line, and predict the output before you run it. Then break the code on purpose and read the compiler's message.

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