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3rdparty/boost_1_81_0/boost/hana/replicate.hpp 2.24 KB
598bfd3f   Hu Chunming   提交_GLIBCXX_USE_CX...
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  /*!
  @file
  Defines `boost::hana::replicate`.
  
  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_REPLICATE_HPP
  #define BOOST_HANA_REPLICATE_HPP
  
  #include <boost/hana/fwd/replicate.hpp>
  
  #include <boost/hana/concept/integral_constant.hpp>
  #include <boost/hana/concept/monad_plus.hpp>
  #include <boost/hana/config.hpp>
  #include <boost/hana/core/dispatch.hpp>
  #include <boost/hana/core/make.hpp>
  #include <boost/hana/cycle.hpp>
  #include <boost/hana/lift.hpp>
  
  #include <cstddef>
  #include <utility>
  
  
  namespace boost { namespace hana {
      //! @cond
      template <typename M>
      template <typename X, typename N>
      constexpr auto replicate_t<M>::operator()(X&& x, N const& n) const {
          using Replicate = BOOST_HANA_DISPATCH_IF(replicate_impl<M>,
              hana::MonadPlus<M>::value &&
              hana::IntegralConstant<N>::value
          );
  
      #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
          static_assert(hana::MonadPlus<M>::value,
          "hana::replicate<M>(x, n) requires 'M' to be a MonadPlus");
  
          static_assert(hana::IntegralConstant<N>::value,
          "hana::replicate<M>(x, n) requires 'n' to be an IntegralConstant");
      #endif
  
          return Replicate::apply(static_cast<X&&>(x), n);
      }
      //! @endcond
  
      template <typename M, bool condition>
      struct replicate_impl<M, when<condition>> : default_ {
          template <typename X, typename N>
          static constexpr auto apply(X&& x, N const& n) {
              return hana::cycle(hana::lift<M>(static_cast<X&&>(x)), n);
          }
      };
  
      template <typename S>
      struct replicate_impl<S, when<Sequence<S>::value>> {
          template <typename X, std::size_t ...i>
          static constexpr auto replicate_helper(X&& x, std::index_sequence<i...>)
          { return hana::make<S>(((void)i, x)...); }
  
          template <typename X, typename N>
          static constexpr auto apply(X&& x, N const&) {
              constexpr std::size_t n = N::value;
              return replicate_helper(static_cast<X&&>(x),
                                      std::make_index_sequence<n>{});
          }
      };
  }} // end namespace boost::hana
  
  #endif // !BOOST_HANA_REPLICATE_HPP