How to limit floats generated by Quickcheck to a range?

I would like to generate random floats for Quickcheck that are limited to a certain range such as 0.0 to 1.0 for testing functions working on probabilities. I would like to be able to do something where this would be successful:

quickcheck! {        
    fn prop(x: f64, y: f64) -> bool {
        assert!(x <= 1.0);
        assert!(y <= 1.0);

        (x * y < x) && (x * y < y)
    }
}