Function core::slice::select::ninther

fn ninther<T, F: FnMut(&T, &T) -> bool>(
    v: &mut [T],
    is_less: &mut F,
    a: usize,
    b: usize,
    c: usize,
    d: usize,
    e: usize,
    f: usize,
    g: usize,
    h: usize,
    i: usize
)

Moves around the 9 elements at the indices a..i, such that v[d] contains the median of the 9 elements and the other elements are partitioned around it.