ext-boost/boost/iterator/advance.hpp
2019-08-24 15:39:04 +02:00

85 lines
2 KiB
C++

// 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/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;
}
}
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;
}
}
}
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