using an index variable for multiple while loops

Question

I have multiple while loops inside a for loop, and I want to use the index of the current loop as the starting value of both while loops like this:

for n in 0..10 {
    let mut j = n;
    while j > 0 {
        j/=2;
    }
    j = n;
    while j > 0 {
        j/=2;
    }
}

I've heard of shadowing but I can't think of a way to have it limited to the inside of the while loop and also be the condition for the while loop. I feel like there should be a better way to do this but I can't find it anywhere. is this really the correct way to do this or is there a nicer way I'm not seeing?

Answer 1

I'm not entirely sure what you intend to do, so if you could edit your question to clarify it, that would help us help you!

Are you looking for a way to not reuse the same j between the two while loops? You could write:

for n in 0..10 {
    let mut j = n;
    while j > 0 {
        j/=2;
    }
    let mut j = n; // That's shadowing.
    while j > 0 {
        j/=2;
    }
}

Answer 2

What exactly is to be achieved is not quite clear. If you want to run through the for loop with a new starting value, use a 'label for the for loop.

'outer: for n in 0..10 {
    let mut j = n;
    if j > 0 {
        while j > 0 {
            j /= 2;
            println!("{j}");
        }
        continue 'outer; 
    }
    j = n;
    if j > 0 {
        while j > 0 {
            j /= 2;
            println!("{j}");
        }
        continue 'outer; 
    }
}

Playground