Linear typing is obviously ideal, but you can also version expensive to clone objects, and use a struct to reference them with a pointer and version number. Th

Linear typing is obviously ideal, but you can also version expensive to clone objects, and use a struct to reference them with a pointer and version number. That way if you mess up your algorithm and attempt to access the old version of an object from a stale reference, you at least get an exception. If you use a struct it makes the pointers fat but there's no allocation.