Loops

https://doc.rust-lang.org/book/loops.html

Loop labels( 条件付きgoto )がよい。 サンプルコードはcontinueだけだったが、breakでも意図通り動く。

fn main() {
    'outer: for x in 0..10 {
        'inner: for y in 0..10 {
            if x % 2 == 0 { continue 'outer; } // continues the loop over x
            if y % 2 == 0 { continue 'inner; } // continues the loop over y
            println!("x: {}, y: {}", x, y);
        }
    }

    'outer2: for x in 0..10 {
        'inner2: for y in 0..10 {
            if x % 2 == 0 { continue 'outer2; } // continues the loop over x
            if x % 5 == 0 { break    'outer2; } // break     the loop over x
            if y % 2 == 0 { continue 'inner2; } // continues the loop over y
            println!("x: {}, y: {}", x, y);
        }
    }
}

$ cargo run
    Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs
     Running `target/debug/4_6_loops`
x: 1, y: 1
x: 1, y: 3
x: 1, y: 5
x: 1, y: 7
x: 1, y: 9
x: 3, y: 1
x: 3, y: 3
x: 3, y: 5
x: 3, y: 7
x: 3, y: 9
x: 5, y: 1
x: 5, y: 3
x: 5, y: 5
x: 5, y: 7
x: 5, y: 9
x: 7, y: 1
x: 7, y: 3
x: 7, y: 5
x: 7, y: 7
x: 7, y: 9
x: 9, y: 1
x: 9, y: 3
x: 9, y: 5
x: 9, y: 7
x: 9, y: 9
x: 1, y: 1
x: 1, y: 3
x: 1, y: 5
x: 1, y: 7
x: 1, y: 9
x: 3, y: 1
x: 3, y: 3
x: 3, y: 5
x: 3, y: 7
x: 3, y: 9