ceph/src/boost/libs/hana/include/boost/hana/monadic_compose.hpp

   1 /*!
   2 @file
   3 Defines `boost::hana::monadic_compose`.
   4
   5 @copyright Louis Dionne 2013-2016
   6 Distributed under the Boost Software License, Version 1.0.
   7 (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
   8  */
   9
  10 #ifndef BOOST_HANA_MONADIC_COMPOSE_HPP
  11 #define BOOST_HANA_MONADIC_COMPOSE_HPP
  12
  13 #include <boost/hana/fwd/monadic_compose.hpp>
  14
  15 #include <boost/hana/chain.hpp>
  16 #include <boost/hana/concept/monad.hpp>
  17 #include <boost/hana/config.hpp>
  18 #include <boost/hana/core/dispatch.hpp>
  19 #include <boost/hana/functional/partial.hpp>
  20
  21
  22 BOOST_HANA_NAMESPACE_BEGIN
  23     namespace detail {
  24         struct monadic_compose_helper {
  25             template <typename F, typename G, typename X>
  26             constexpr decltype(auto) operator()(F&& f, G&& g, X&& x) const {
  27                 using M = typename hana::tag_of<decltype(g(x))>::type;
  28
  29             #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
  30                 static_assert(hana::Monad<M>::value,
  31                 "hana::monadic_compose(f, g) requires 'g' to return a monadic value");
  32             #endif
  33
  34                 return hana::chain(static_cast<G&&>(g)(static_cast<X&&>(x)),
  35                                    static_cast<F&&>(f));
  36             }
  37         };
  38     }
  39
  40     //! @cond
  41     template <typename F, typename G>
  42     constexpr auto monadic_compose_t::operator()(F&& f, G&& g) const {
  43         return hana::partial(detail::monadic_compose_helper{},
  44             static_cast<F&&>(f),
  45             static_cast<G&&>(g)
  46         );
  47     }
  48     //! @endcond
  49 BOOST_HANA_NAMESPACE_END
  50
  51 #endif // !BOOST_HANA_MONADIC_COMPOSE_HPP