text: /*!
  @file
  Defines `boost::hana::monadic_compose`.
  
  @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)
   */
  
  #ifndef BOOST_HANA_MONADIC_COMPOSE_HPP
  #define BOOST_HANA_MONADIC_COMPOSE_HPP
  
  #include <boost/hana/fwd/monadic_compose.hpp>
  
  #include <boost/hana/chain.hpp>
  #include <boost/hana/concept/monad.hpp>
  #include <boost/hana/config.hpp>
  #include <boost/hana/core/dispatch.hpp>
  #include <boost/hana/functional/partial.hpp>
  
  
  BOOST_HANA_NAMESPACE_BEGIN
      namespace detail {
          struct monadic_compose_helper {
              template <typename F, typename G, typename X>
              constexpr decltype(auto) operator()(F&& f, G&& g, X&& x) const {
                  using M = typename hana::tag_of<decltype(g(x))>::type;
  
              #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
                  static_assert(hana::Monad<M>::value,
                  "hana::monadic_compose(f, g) requires 'g' to return a monadic value");
              #endif
  
                  return hana::chain(static_cast<G&&>(g)(static_cast<X&&>(x)),
                                     static_cast<F&&>(f));
              }
          };
      }
  
      //! @cond
      template <typename F, typename G>
      constexpr auto monadic_compose_t::operator()(F&& f, G&& g) const {
          return hana::partial(detail::monadic_compose_helper{},
              static_cast<F&&>(f),
              static_cast<G&&>(g)
          );
      }
      //! @endcond
  BOOST_HANA_NAMESPACE_END
  
  #endif // !BOOST_HANA_MONADIC_COMPOSE_HPP
  