text: // Copyright Louis Dionne 2013-2016
  // Distributed under the Boost Software License, Version 1.0.
  // (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
  
  #include <boost/hana.hpp>
  
  #include <iostream>
  #include <string>
  #include <type_traits>
  #include <utility>
  namespace hana = boost::hana;
  using namespace std::literals;
  
  
  //! [utilities]
  template <typename Xs>
  std::string join(Xs&& xs, std::string sep) {
    return hana::fold(hana::intersperse(std::forward<Xs>(xs), sep), "", hana::_ + hana::_);
  }
  
  std::string quote(std::string s) { return "\"" + s + "\""; }
  
  template <typename T>
  auto to_json(T const& x) -> decltype(std::to_string(x)) {
    return std::to_string(x);
  }
  
  std::string to_json(char c) { return quote({c}); }
  std::string to_json(std::string s) { return quote(s); }
  //! [utilities]
  
  //! [Struct]
  template <typename T>
    std::enable_if_t<hana::Struct<T>::value,
  std::string> to_json(T const& x) {
    auto json = hana::transform(hana::keys(x), [&](auto name) {
      auto const& member = hana::at_key(x, name);
      return quote(hana::to<char const*>(name)) + " : " + to_json(member);
    });
  
    return "{" + join(std::move(json), ", ") + "}";
  }
  //! [Struct]
  
  //! [Sequence]
  template <typename Xs>
    std::enable_if_t<hana::Sequence<Xs>::value,
  std::string> to_json(Xs const& xs) {
    auto json = hana::transform(xs, [](auto const& x) {
      return to_json(x);
    });
  
    return "[" + join(std::move(json), ", ") + "]";
  }
  //! [Sequence]
  
  
  int main() {
  //! [usage]
  struct Car {
    BOOST_HANA_DEFINE_STRUCT(Car,
      (std::string, brand),
      (std::string, model)
    );
  };
  
  struct Person {
    BOOST_HANA_DEFINE_STRUCT(Person,
      (std::string, name),
      (std::string, last_name),
      (int, age)
    );
  };
  
  Car bmw{"BMW", "Z3"}, audi{"Audi", "A4"};
  Person john{"John", "Doe", 30};
  
  auto tuple = hana::make_tuple(john, audi, bmw);
  std::cout << to_json(tuple) << std::endl;
  //! [usage]
  }
  