loop - rust-course

The loop statement defines an infinite loop.

As an example, the following loop would never end:

loop {
  println!("Hello!");
}

10.2.1break¶

Using the break keyword, we may leave the loop at any moment:

let mut i = 0;
loop {
  if i > 4 {
    break;
  }
  print!("{i}, ");
  i += 1;
}

()

The break keyword allows us to return a value:

let mut i = 0;
let n = loop {
  if i > 3 {
    break 15;
  }
  i += 1;
};
n

15

Using the continue keyword, we can also skip the current step and go to the next:

let mut i = 0;
loop {
  i += 1;
  if i % 2 == 0 {
    continue;
  }
  if i > 8 {
    break;
  }
  print!("{i}, ");
}

()

Exiting from nested loops is best done using a label:

let mut i = 0;
let mut j = 0;
'my_label: loop {
  i += 1;
  loop {
    j += 1;
    if i+j > 7 {
      break 'my_label;
    }
  }
}
(i, j)

(1, 7)