Strange behavior in nested while loops

[cbens]

Can somebody explain what is going on in the following code; is it a bug or a language feature that the loops appear to exit early?

fn main() {
    let mut y = 0.0;
    let mut x = 0.0;
    while y < 4.0 {
        while x < 4.0 {
            println!("{}, {}", x, y);
            x+=1.0;
        }
        y+=1.0;
    }
    println!("{}, {}", x, y);
}

results in this output

0, 0
1, 0
2, 0
3, 0
4, 4

Rust Playground

[leonardo]

Move the initialization of x inside the outer while loop.

[kyrias]

What exactly makes you think it's exiting early?

[kapoira]

0, 0
1, 0
2, 0
3, 0
4, 4

The code is doing what have to do. 3 println after that increases the y four times (without println anything), and the last println

[cbens]

Doh; thanks