1// Copyright (C) 2017 Michel Morin.
2//
3// Distributed under the Boost Software License, Version 1.0.
4// (See accompanying file LICENSE_1_0.txt or copy at
5// http://www.boost.org/LICENSE_1_0.txt)
6
7#ifndef BOOST_ITERATOR_ADVANCE_HPP
8#define BOOST_ITERATOR_ADVANCE_HPP
9
10#include <boost/config.hpp>
11#include <boost/iterator/iterator_categories.hpp>
12
13namespace boost {
14namespace iterators {
15
16 namespace detail {
17 template <typename InputIterator, typename Distance>
18 inline BOOST_CXX14_CONSTEXPR void
19 advance_impl(
20 InputIterator& it
21 , Distance n
22 , incrementable_traversal_tag
23 )
24 {
25 while (n > 0) {
26 ++it;
27 --n;
28 }
29 }
30
31 template <typename BidirectionalIterator, typename Distance>
32 inline BOOST_CXX14_CONSTEXPR void
33 advance_impl(
34 BidirectionalIterator& it
35 , Distance n
36 , bidirectional_traversal_tag
37 )
38 {
39 if (n >= 0) {
40 while (n > 0) {
41 ++it;
42 --n;
43 }
44 }
45 else {
46 while (n < 0) {
47 --it;
48 ++n;
49 }
50 }
51 }
52
53 template <typename RandomAccessIterator, typename Distance>
54 inline BOOST_CXX14_CONSTEXPR void
55 advance_impl(
56 RandomAccessIterator& it
57 , Distance n
58 , random_access_traversal_tag
59 )
60 {
61 it += n;
62 }
63 }
64
65 namespace advance_adl_barrier {
66 template <typename InputIterator, typename Distance>
67 inline BOOST_CXX14_CONSTEXPR void
68 advance(InputIterator& it, Distance n)
69 {
70 detail::advance_impl(
71 it, n, typename iterator_traversal<InputIterator>::type()
72 );
73 }
74 }
75
76 using namespace advance_adl_barrier;
77
78} // namespace iterators
79
80using namespace iterators::advance_adl_barrier;
81
82} // namespace boost
83
84#endif
85

source code of include/boost/iterator/advance.hpp