#include <iostream>
#include <unordered_map>
#include <boost/utility/string_view.hpp>
#include <boost/functional/hash.hpp>

using namespace std;

class Hasher {
 public:
  std::size_t operator()(boost::string_view str) const {
    return boost::hash_range<const char*>(str.begin(), str.end());
  }
};

int main() {
  std::unordered_map<boost::string_view, std::size_t, Hasher> m;

  m["abc"] = 123;
  m["def"] = 456;

  for (auto& elem : m)
    std::cout << elem.first << ":" << elem.second << std::endl;

  return 0;
}