Question

currently I’m struggling with maps which should contain themselves. But I don’t know the depth of the nesting when compiling.

std::map<Key, std::map<Key, std::map<Key, std::map<Key, ...>>>>

Is there a way to achieve this goal without infinitely repeating myself?

Answer 1

The golden hammer for self-referential data structures is the use of pointers. In your particular, case, to implement a tree you can just do that:

template <typename Key, typename Value>
struct Node {
   Value data;
   std::map< Key, std::shared_ptr<Node> > child;
// ...
};

Each node in the tree contains a value and a set of child Nodes maintained though a map of shared pointers. The std::map requires (according to the standard) the stored types to be complete, but shared_ptr only needs the type to be complete at the point of creation which allows this data structure. A plain Node* would also have worked, but then you would have to manage the memory manually.