text: // Copyright Louis Dionne 2013-2017
  // 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/assert.hpp>
  #include <boost/hana/equal.hpp>
  #include <boost/hana/integral_constant.hpp>
  #include <boost/hana/string.hpp>
  #include <boost/hana/map.hpp>
  #include <boost/hana/type.hpp>
  #include <boost/hana/union.hpp>
  
  #include <string>
  namespace hana = boost::hana;
  using namespace hana::literals;
  
  
  static auto m1 = hana::make_map(
      hana::make_pair(BOOST_HANA_STRING("key1"), hana::type_c<std::string>),
      hana::make_pair(BOOST_HANA_STRING("key2"), hana::type_c<std::string>)
  );
  
  static auto m2 = hana::make_map(
      hana::make_pair(BOOST_HANA_STRING("key3"), hana::type_c<std::string>),
      hana::make_pair(BOOST_HANA_STRING("key4"), hana::type_c<std::string>),
      hana::make_pair(BOOST_HANA_STRING("key5"), hana::type_c<std::string>)
  );
  
  BOOST_HANA_CONSTANT_CHECK(hana::union_(m1, m2) == hana::make_map(
         hana::make_pair(BOOST_HANA_STRING("key1"), hana::type_c<std::string>),
         hana::make_pair(BOOST_HANA_STRING("key2"), hana::type_c<std::string>),
         hana::make_pair(BOOST_HANA_STRING("key3"), hana::type_c<std::string>),
         hana::make_pair(BOOST_HANA_STRING("key4"), hana::type_c<std::string>),
         hana::make_pair(BOOST_HANA_STRING("key5"), hana::type_c<std::string>)
  ));
  
  constexpr auto m3 = hana::make_map(
      hana::make_pair(hana::type_c<int>, hana::int_c<1>),
      hana::make_pair(hana::type_c<bool>, hana::bool_c<true>)
  );
  
  constexpr auto m4 = hana::make_map(
         hana::make_pair(hana::type_c<char>, hana::char_c<'c'>),
         hana::make_pair(hana::type_c<bool>, hana::bool_c<false>)
  );
  
  BOOST_HANA_CONSTANT_CHECK(hana::union_(m3, m4) == hana::make_map(
         hana::make_pair(hana::type_c<int>, hana::int_c<1>),
         hana::make_pair(hana::type_c<bool>, hana::bool_c<false>),
         hana::make_pair(hana::type_c<char>, hana::char_c<'c'>)
  ));
  
  int main() { }
  