Macro doe::snail_sort

macro_rules! snail_sort {
    ($vec:expr) => { ... };
}

return the array elements arranged from outermost elements to the middle element, traveling clockwise (n x n)

use doe::*;
let v1 = snail_sort!(vec![vec![1, 2, 3], vec![4, 5, 6], vec![7, 8, 9]]);
let v2 =  snail_sort!(vec![vec![1.1, 2.1, 3.1],vec![4.1, 5.1, 6.1],vec![7.1, 8.1, 9.1]]);
assert_eq!(vec![1, 2, 3, 6, 9, 8, 7, 4, 5], v1);
assert_eq!(vec![1.1, 2.1, 3.1, 6.1, 9.1, 8.1, 7.1, 4.1, 5.1], v2);