Rust/loop/label

• when loops are nested in rust, it's possible to lablel them. This is useful if you have to break out of one loop but the other.
• The syntax is 'loop_name: loop { ... break 'loop_name}.
  • Confus/ing
    • Syntactically, the ('identifier) token shape appears elsewhere in Rust/Lifetimes, but there it serves a different purpose

    • Context	Meaning
      'label: before a loop	loop label
      'label in break 'label	labeled control flow
      'a in &'a T	lifetime parameter
      'static	the static lifetime
      '_'	anonymous lifetime

    • So 'thing is not “the same feature” being reused — it’s the same token class used in multiple grammar positions.
• Example
  • rust

    fn loop_labels_to_disambiguate_multiple_loops() {
        println!("Loop labels to disambiguate multiple loops:");
        let mut count = 0;
    
        'counting_up: loop {
            println!("count = {count}");
            let mut remaining = 10;
    
            loop {
                println!("remaining = {remaining}");
                if remaining == 9 {
                    break;
                }
                if count == 2 {
                    break 'counting_up;
                }
                remaining -= 1;
            }
    
            count += 1;
        }
        println!("End count = {count}");
    }