boost/hana/chain.hpp

0001 /*!
0002 @file
0003 Defines `boost::hana::chain`.
0004
0005 Copyright Louis Dionne 2013-2022
0006 Distributed under the Boost Software License, Version 1.0.
0007 (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
0008  */
0009
0010 #ifndef BOOST_HANA_CHAIN_HPP
0011 #define BOOST_HANA_CHAIN_HPP
0012
0013 #include <boost/hana/fwd/chain.hpp>
0014
0015 #include <boost/hana/concept/monad.hpp>
0016 #include <boost/hana/config.hpp>
0017 #include <boost/hana/core/dispatch.hpp>
0018 #include <boost/hana/flatten.hpp>
0019 #include <boost/hana/transform.hpp>
0020
0021
0022 namespace boost { namespace hana {
0023     //! @cond
0024     template <typename Xs, typename F>
0025     constexpr decltype(auto) chain_t::operator()(Xs&& xs, F&& f) const {
0026         using M = typename hana::tag_of<Xs>::type;
0027         using Chain = BOOST_HANA_DISPATCH_IF(chain_impl<M>,
0028             hana::Monad<M>::value
0029         );
0030
0031     #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
0032         static_assert(hana::Monad<M>::value,
0033         "hana::chain(xs, f) requires 'xs' to be a Monad");
0034     #endif
0035
0036         return Chain::apply(static_cast<Xs&&>(xs), static_cast<F&&>(f));
0037     }
0038     //! @endcond
0039
0040     template <typename M, bool condition>
0041     struct chain_impl<M, when<condition>> : default_ {
0042         template <typename Xs, typename F>
0043         static constexpr auto apply(Xs&& xs, F&& f) {
0044             return hana::flatten(hana::transform(static_cast<Xs&&>(xs),
0045                                                  static_cast<F&&>(f)));
0046         }
0047     };
0048 }} // end namespace boost::hana
0049
0050 #endif // !BOOST_HANA_CHAIN_HPP