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3rdparty/boost_1_81_0/boost/hana/ap.hpp 2.45 KB
598bfd3f   Hu Chunming   提交_GLIBCXX_USE_CX...
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  /*!
  @file
  Defines `boost::hana::ap`.
  
  Copyright Louis Dionne 2013-2022
  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_AP_HPP
  #define BOOST_HANA_AP_HPP
  
  #include <boost/hana/fwd/ap.hpp>
  
  #include <boost/hana/chain.hpp>
  #include <boost/hana/concept/applicative.hpp>
  #include <boost/hana/concept/sequence.hpp>
  #include <boost/hana/config.hpp>
  #include <boost/hana/core/dispatch.hpp>
  #include <boost/hana/detail/variadic/foldl1.hpp>
  #include <boost/hana/functional/curry.hpp>
  #include <boost/hana/functional/partial.hpp>
  #include <boost/hana/transform.hpp>
  
  
  namespace boost { namespace hana {
      template <typename A, bool condition>
      struct ap_impl<A, when<condition>> : default_ {
          template <typename ...Args>
          static constexpr auto apply(Args&& ...args) = delete;
      };
  
      //! @cond
      template <typename F, typename X>
      constexpr decltype(auto) ap_t::operator()(F&& f, X&& x) const {
          using Function = typename hana::tag_of<F>::type;
          using Value = typename hana::tag_of<X>::type;
          using Ap = BOOST_HANA_DISPATCH_IF(ap_impl<Function>,
              hana::Applicative<Function>::value && hana::Applicative<Value>::value
          );
  
      #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
          static_assert(hana::Applicative<Function>::value,
          "hana::ap(f, x) requires 'f' to be an Applicative");
  
          static_assert(hana::Applicative<Value>::value,
          "hana::ap(f, x) requires 'x' to be an Applicative");
      #endif
  
          return Ap::apply(static_cast<F&&>(f), static_cast<X&&>(x));
      }
  
      template <typename F, typename ...Xs>
      constexpr decltype(auto) ap_t::operator()(F&& f, Xs&& ...xs) const {
          static_assert(sizeof...(xs) >= 1,
          "hana::ap must be called with at least two arguments");
  
          return detail::variadic::foldl1(
              *this,
              hana::transform(static_cast<F&&>(f), hana::curry<sizeof...(xs)>),
              static_cast<Xs&&>(xs)...
          );
      }
      //! @endcond
  
      template <typename S>
      struct ap_impl<S, when<Sequence<S>::value>> {
          template <typename F, typename X>
          static constexpr decltype(auto) apply(F&& f, X&& x) {
              return hana::chain(
                  static_cast<F&&>(f),
                  hana::partial(hana::transform, static_cast<X&&>(x))
              );
          }
      };
  }} // end namespace boost::hana
  
  #endif // !BOOST_HANA_AP_HPP