#include <memory>
#include <boost/multi_index_container.hpp>
#include <boost/multi_index/ordered_index.hpp>
#include <boost/multi_index/key_extractors.hpp>
#include <boost/multi_index/hashed_index.hpp>

struct element
{
  element(int a, float b) : x(a) , y(b) {}

  int x;
  float y;
};

struct A
{
  using container = boost::multi_index_container<
    std::unique_ptr<element>,
    boost::multi_index::indexed_by<
      boost::multi_index::ordered_unique<
        boost::multi_index::composite_key<
          boost::multi_index::member<element, const int, &element::x>,
          boost::multi_index::member<element, const float, &element::y>
          >
        >
      >
    >;

  container ints;
};

int main() {
  A a;
  a.ints.insert(std::make_unique<element>(5, 4.0));

  return 0;
}