diag

import mir.ndslice.topology : iota;
import mir.ndslice.slice : sliced;

//  -------
// | 0 1 2 |
//  -------
auto a = iota(3).diag;
auto result = [[0, 0, 0],
               [0, 1, 0],
               [0, 0, 2]].sliced;
assert(a[0] == result[0]);
assert(a[1] == result[1]);
assert(a[2] == result[2]);