pub fn blank(self: Self) u64 {

pub fn empty(self: Self) u64 {

    return self.head.mask() & self.neck.blank() == 0;

    return self.head.mask() & self.neck.empty() == 0;

pub fn empty(self:Self) u64 {
    return self.neck.blank() & ~self.head.mask();

pub fn empty(self: Self) u64 {
    return self.neck.empty() & ~self.head.mask();