// Rust uses row major addressing for arrays
// It does not use row major for vectors.
fn main() {
    // rust uses row major in arrays
    let aa = [[1,2,3], [4,5,6],[7,8,9], [10,11,12]];
    for i in 0..4 {
        for j in 0..3 {
            let raw_pointer_a = &aa[i][j] as *const i32 as u64;
            println!("{} {}: {}",i,j,raw_pointer_a);
        }
    }

    // now create a fill an vector of vectors
    let mut aa: Vec<Vec<i32>> = vec![];
    for ii in 0..5 {
        let mut bb = vec![];
        for jj in 0..500 {
            bb.push(jj);
        }
        aa.push(bb);
    }
    // show location in memory of each sub vector.
    // no matter how much is in the sub vector, it is 24 bytes
    for i in 0..4 {
        let rpa = &aa[i] as *const Vec<i32> as u64;
        println!("vec of vecs {} {}", i, rpa);
    }
}