Looping in Rust

To execute a code block more than once, we can use loops. There are 3 ways to do this in Rust:

• loop
• while
• for

Repetition with Loop

We can use loop like this.

Warning! this program will keep running , unless you stop it manually

fn main() {
    loop {
        println!("yeayyy!");
    }
}

It’s a common mistake on programming, when we write loop without condition.

ALWAYS tell your loop when to stop. We can use break keyword to stop the program.

fn main() {
    let mut counter = 0;

    let result = loop {
    	//value must be changed, to meet certain codition
        counter += 1;
		
        //We use if condition to stop the loop after 10
        if counter == 10 {
            break counter * 2;
        }
    };

    println!("The result is {}", result);
}

Repetition with While

We can also explicitly write the condition after while keyword.

fn main() {
    let mut number = 3;

    while number != 0 {
        println!("{}!", number);
		//change value on each loop
        number -= 1;
    }

    println!("LIFTOFF!!!");
}

Repetition with For

For loop is perfect if we want to iterate an array, to prevent out of index error

fn main() {
    let a = [10, 20, 30, 40, 50];

    for element in a.iter() {
        println!("the value is: {}", element);
    }
}

This way when we change the array, we don’t need to update how many times it should repeat.

Reverse with for

We can reverse order of number with .rev()

fn main() {
    for number in (1..4).rev() {
        println!("{}!", number);
    }
    println!("gooo!");
}

result

3!
2!
1!
gooo!