To implement `iterator_to` for anything except `vector`, you have to rely on a cast like this:

struct Node {

    T t;

    Node *next;

};

Node *node_from_t(T *t) {

    return reinterpret_cast<Node *>(t);

}

int main() {

    Node n;

    assert(node_from_t(&n.t) == &n);

}

I'm not sure if this is well-defined. As long as `t` is the first member of `Node`, I think it might actually be well-defined; but I wouldn't bet money on it.

Problem is, library implementors tend to be extremely loath to rely on anything smelling of UB in their implementations.

my $.02,

–Arthur