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3rdparty/boost_1_81_0/boost/iterator/advance.hpp 2.32 KB
63e88f80   Hu Chunming   提交三方库
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  // Copyright (C) 2017 Michel Morin.
  //
  // Distributed under the Boost Software License, Version 1.0.
  // (See accompanying file LICENSE_1_0.txt or copy at
  // http://www.boost.org/LICENSE_1_0.txt)
  
  #ifndef BOOST_ITERATOR_ADVANCE_HPP
  #define BOOST_ITERATOR_ADVANCE_HPP
  
  #include <boost/config.hpp>
  #include <boost/detail/workaround.hpp>
  #include <boost/iterator/iterator_categories.hpp>
  
  namespace boost {
  namespace iterators {
  
      namespace detail {
          template <typename InputIterator, typename Distance>
          inline BOOST_CXX14_CONSTEXPR void
          advance_impl(
              InputIterator& it
            , Distance n
            , incrementable_traversal_tag
          )
          {
              while (n > 0) {
                  ++it;
                  --n;
              }
          }
  
  #if BOOST_WORKAROUND(BOOST_GCC_VERSION, >= 40600)
  // type-limits warning issued below when n is an unsigned integral
  #pragma GCC diagnostic push
  #pragma GCC diagnostic ignored "-Wtype-limits"
  #endif
  
          template <typename BidirectionalIterator, typename Distance>
          inline BOOST_CXX14_CONSTEXPR void
          advance_impl(
              BidirectionalIterator& it
            , Distance n
            , bidirectional_traversal_tag
          )
          {
              if (n >= 0) {
                  while (n > 0) {
                      ++it;
                      --n;
                  }
              }
              else {
                  while (n < 0) {
                      --it;
                      ++n;
                  }
              }
          }
  
  #if BOOST_WORKAROUND(BOOST_GCC_VERSION, >= 40600)
  #pragma GCC diagnostic pop
  #endif
  
          template <typename RandomAccessIterator, typename Distance>
          inline BOOST_CXX14_CONSTEXPR void
          advance_impl(
              RandomAccessIterator& it
            , Distance n
            , random_access_traversal_tag
          )
          {
              it += n;
          }
      }
  
      namespace advance_adl_barrier {
          template <typename InputIterator, typename Distance>
          inline BOOST_CXX14_CONSTEXPR void
          advance(InputIterator& it, Distance n)
          {
              detail::advance_impl(
                  it, n, typename iterator_traversal<InputIterator>::type()
              );
          }
      }
  
      using namespace advance_adl_barrier;
  
  } // namespace iterators
  
  using namespace iterators::advance_adl_barrier;
  
  } // namespace boost
  
  #endif