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Comment by radarsat1 | Hacker News Reader

Since memory is copied, it's really not clear to me what the advantage is of using value_ptr over just using values.

Is it just about heap vs. stack?

I think its about recursive types/members, e.g.

    class Tree { Tree _left, _right; };

Won't compile because it has an infinite size. However

    class Tree { Tree *_left, *_right; };

Compiles, but the author contends that a more explicit description of the ownership semantics is better:

    class Tree { value_ptr<Tree> _left, _right; }

This is also why `value_ptr` is different than `optional`.

I think you have to say something about the copy semantics too, because if you ignore those, value_ptr would be synonymous with unique_ptr.

   class Tree { Tree *_left, *_right; };
   Tree y = x;

makes a shallow copy.

   class Tree { unique_ptr<Tree> _left, _right; };
   Tree y = x;

doesn't compile, but

   class Tree { value_ptr<Tree> _left, _right; };
   Tree y = x;

makes a deep copy.

With value-ptr's would traversing the tree require making copies of examined nodes as you search? What would the tree_search method look like?