Loops

Rust has three kinds of loops:
1. loop - Infinite Loop, uses break and continue
2. while - Breaks when the condition doesn't meet.
3. for - Faster and easier to use for iterators and classical for loops.

Simple Infinite Loop:


#![allow(unused)]
fn main() {
loop {
  // Do something iteratively
}
}

Named Loop


#![allow(unused)]
fn main() {
'outer:loop {
 loop {
  break 'outer;
 }
}
}

Named Loop with different breaks:


#![allow(unused)]
fn main() {
'oulter_loop: loop {
  loop {
    if condition {
      break 'oulter_loop; // Breaks Outer Loop
    }

    if some_other_condition {
      break; // Breaks Inner Loop
    }
  }
}
}

Returning values in loops:


fn main() {
    let mut counter = 0;

    let result = loop {
        counter += 1;

        if counter == 10 {
            break counter * 2;
        }
    };

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

The while loop:


fn main() {
    let mut number = 3;

    // Prevents the use of break, by including the condition with while
    while number != 0 {
        println!("{}!", number);

        number -= 1;
    }

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

The for loop:


#![allow(unused)]
fn main() {
// Last item in exclusive, or 0..10 === 0..=9
for x in 0..10 {
    println!("{}", x); // x: i32
}
}

The for loop for iterator:


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

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

A for loop for iterating characters in String


#![allow(unused)]
fn main() {
for c in name.chars() {
    // c variable stores one charater per iteration
}
}

Enumeration


#![allow(unused)]
fn main() {
for (i, v) in request.chars().enumerate() {
    // i is index, v is variable
}
}

The for loop in reverse:


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

// Output:
// 3!
// 2!
// 1!
// LIFTOFF!!!