Function rank_impl

fn rank_impl<T, C, E>(
    len: usize,
    valid: Vec<(T, u32)>,
    options: SortOptions,
    compare: C,
    eq: E,
) -> Vec<u32>
where
    T: Copy,
    C: Fn(T, T) -> Ordering,
    E: Fn(T, T) -> bool,