Rust - Loop

Loop

Loop of rust is very similar with python's loop.
We can use loop, while, for to make loop

Loop

loop is very simple infinite loop in rust.

fn main() {
	let mut counter = 0;
    loop {
    	counter += 1;
        println!("counter is {}", counter);
        if counter > 10 {
        	break;
        }
    }
}

Like the example above, loop doesn't have conditional so we have to break it manually. This is quite simple but not rusty style.
We can give a loop a name to tell the break statement which loop to break.

fn main() {
  let mut counter = 0;
  let mut counter2 = 0;
  'first: loop {
    counter += 1;
    println!("the counter is: {}", counter);
    if counter > 9 {
      println!("now entering the second loop");

      'second: loop {
        println!("second counter is: {}", counter2);
        counter2 += 1;
        if counter2 == 3 {
          break 'first;
        }
      }
    }
  }
}

This is the example of naming the loops. The break statement telling that it will break the first(outer) loop.

while

while is also same as the while of python.

  counter = 0;
  while counter != 5 {
    counter += 1;
    println!("{}", counter);
  }

Also we can think it's loop + conditional expression.

for

Rust's for is same as the python's for. We use for..in expression.

for number in 0..3 {
	println!("{}", number);
}

Also we have range expression(Definitely same as python).
When we use 0..3, it means 0 1 2 (from 0, before 3), 0..=3 means 0 1 2 3 (from 0 to 3).

Like loop, we can also give a name to while, for loop.
And when we break the loop, we can return some value by break statement.

  // break can have return value
  counter = 5;

  let number = loop {
    counter += 1;
    if counter %53 == 3 {
      break counter;
    }
  };
  println!("number is now: {}", number);

Like this example assigning the value to variable, we can send a return value when we break the loop.