function f(
    a, // bitmask representing all queens are placed
    b, // result storage
    c, // positions record
    d, // row
    e, // left diagnal
    g, // right diagnal
    h, // placeholder for places where queens can be placed in
    i  // placeholder for the position where the queen is placed in
) {
    for (a ^ d ? h = a & ~(d | e | g) : b.push(c); i = -h & h; h ^= i) // loop through over the subtrees
        f(a, b || (b = []), d ? c + [,i] : i, d | i, (e | i) << 1, (g | i) >> 1); // go to the next depth
    return b;
}