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_DISTANCE_HPP
#define BOOST_ITERATOR_DISTANCE_HPP
#include <boost/config.hpp>
#include <boost/iterator/iterator_categories.hpp>
#include <boost/iterator/iterator_traits.hpp>
namespace boost {
namespace iterators {
namespace detail {
template <typename SinglePassIterator>
inline BOOST_CXX14_CONSTEXPR typename iterator_difference<SinglePassIterator>::type
distance_impl(
SinglePassIterator first
, SinglePassIterator last
, single_pass_traversal_tag
)
{
typename iterator_difference<SinglePassIterator>::type n = 0;
while (first != last) {
++first;
++n;
}
return n;
}
template <typename RandomAccessIterator>
inline BOOST_CXX14_CONSTEXPR typename iterator_difference<RandomAccessIterator>::type
distance_impl(
RandomAccessIterator first
, RandomAccessIterator last
, random_access_traversal_tag
)
{
return last - first;
}
}
namespace distance_adl_barrier {
template <typename SinglePassIterator>
inline BOOST_CXX14_CONSTEXPR typename iterator_difference<SinglePassIterator>::type
distance(SinglePassIterator first, SinglePassIterator last)
{
return detail::distance_impl(
first, last, typename iterator_traversal<SinglePassIterator>::type()
);
}
}
using namespace distance_adl_barrier;
} // namespace iterators
using namespace iterators::distance_adl_barrier;
} // namespace boost
#endif
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