C++ container of iterators and circular references

Question

I'd like to create two containers that contain iterators to each other. I'd like to do this hopefully without introducing any intermediate/indirect types. Is this possible or do iterator types depending on knowing the size of the container's data type?

Here is some sample code that I'd like to get compiling:

#include <map>
#include <deque>
#include <string>

class mapvalue_t
{
  public:
    std::deque< std::map<std::string,mapvalue_t>::iterator  >::iterator i;
};

typedef std::map<std::string,mapvalue_t> maptype_t;
typedef std::deque< maptype_t::iterator > queuetype_t;

int main(void)
{
  maptype_t m;
  queuetype_t q;
}

Never mind, it compiles now. I had a queue there, rather than my intended deque :)

Answer 1

This works if you use a deque instead of a queue. Queue is not a container, but a facade so it does not support the ::iterator call.

From cplusplus.com:

queues are implemented as containers adaptors, which are classes that use an encapsulated object of a specific container class as its underlying container, providing a specific set of member functions to access it elements. Elements are pushed into the "back" of the specific container and popped from its "front".

Answer 2

You should be very careful about storing iterators. Modifying the collection can easily invalidate all iterators. You would be far better storing an id or a (managed) pointer.