ceph/src/boost/boost/hana/extend.hpp

   1 /*!
   2 @file
   3 Defines `boost::hana::extend`.
   4
   5 @copyright Louis Dionne 2013-2017
   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_EXTEND_HPP
  11 #define BOOST_HANA_EXTEND_HPP
  12
  13 #include <boost/hana/fwd/extend.hpp>
  14
  15 #include <boost/hana/concept/comonad.hpp>
  16 #include <boost/hana/config.hpp>
  17 #include <boost/hana/core/dispatch.hpp>
  18 #include <boost/hana/duplicate.hpp>
  19 #include <boost/hana/transform.hpp>
  20
  21
  22 BOOST_HANA_NAMESPACE_BEGIN
  23     //! @cond
  24     template <typename W_, typename F>
  25     constexpr decltype(auto) extend_t::operator()(W_&& w, F&& f) const {
  26         using W = typename hana::tag_of<W_>::type;
  27         using Extend = BOOST_HANA_DISPATCH_IF(extend_impl<W>,
  28             hana::Comonad<W>::value
  29         );
  30
  31     #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
  32         static_assert(hana::Comonad<W>::value,
  33         "hana::extend(w, f) requires 'w' to be a Comonad");
  34     #endif
  35
  36         return Extend::apply(static_cast<W_&&>(w), static_cast<F&&>(f));
  37     }
  38     //! @endcond
  39
  40     template <typename W, bool condition>
  41     struct extend_impl<W, when<condition>> : default_ {
  42         template <typename X, typename F>
  43         static constexpr decltype(auto) apply(X&& x, F&& f) {
  44             return hana::transform(hana::duplicate(static_cast<X&&>(x)),
  45                                    static_cast<F&&>(f));
  46         }
  47     };
  48 BOOST_HANA_NAMESPACE_END
  49
  50 #endif // !BOOST_HANA_EXTEND_HPP