#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());
  }
  void check() const
  {
    m["abc"] = 123;
    m["def"] = 456;
    for (auto& elem : m)
      std::cout << elem.first << ":" << elem.second << std::endl;
  }
 private:
  std::unordered_map<boost::string_view, std::size_t, Hasher> m;

};

int main() {
  Hasher p;
  p.check();
  return 0;
}