1 // -*- C++ -*-
2 //===----------------------------------------------------------------------===//
3 //
4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5 // See https://llvm.org/LICENSE.txt for license information.
6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //
8 //===----------------------------------------------------------------------===//
9
10 #ifndef _LIBCPP___ITERATOR_DISTANCE_H
11 #define _LIBCPP___ITERATOR_DISTANCE_H
12
13 #include <__config>
14 #include <__iterator/concepts.h>
15 #include <__iterator/incrementable_traits.h>
16 #include <__iterator/iterator_traits.h>
17 #include <__ranges/access.h>
18 #include <__ranges/concepts.h>
19 #include <__ranges/size.h>
20 #include <type_traits>
21
22 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
23 # pragma GCC system_header
24 #endif
25
26 _LIBCPP_BEGIN_NAMESPACE_STD
27
28 template <class _InputIter>
29 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
30 typename iterator_traits<_InputIter>::difference_type
__distance(_InputIter __first,_InputIter __last,input_iterator_tag)31 __distance(_InputIter __first, _InputIter __last, input_iterator_tag)
32 {
33 typename iterator_traits<_InputIter>::difference_type __r(0);
34 for (; __first != __last; ++__first)
35 ++__r;
36 return __r;
37 }
38
39 template <class _RandIter>
40 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
41 typename iterator_traits<_RandIter>::difference_type
__distance(_RandIter __first,_RandIter __last,random_access_iterator_tag)42 __distance(_RandIter __first, _RandIter __last, random_access_iterator_tag)
43 {
44 return __last - __first;
45 }
46
47 template <class _InputIter>
48 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
49 typename iterator_traits<_InputIter>::difference_type
distance(_InputIter __first,_InputIter __last)50 distance(_InputIter __first, _InputIter __last)
51 {
52 return _VSTD::__distance(__first, __last, typename iterator_traits<_InputIter>::iterator_category());
53 }
54
55 #if _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
56
57 // [range.iter.op.distance]
58
59 namespace ranges {
60 namespace __distance {
61
62 struct __fn {
63 template<class _Ip, sentinel_for<_Ip> _Sp>
64 requires (!sized_sentinel_for<_Sp, _Ip>)
65 _LIBCPP_HIDE_FROM_ABI
operator__fn66 constexpr iter_difference_t<_Ip> operator()(_Ip __first, _Sp __last) const {
67 iter_difference_t<_Ip> __n = 0;
68 while (__first != __last) {
69 ++__first;
70 ++__n;
71 }
72 return __n;
73 }
74
75 template<class _Ip, sized_sentinel_for<decay_t<_Ip>> _Sp>
76 _LIBCPP_HIDE_FROM_ABI
operator__fn77 constexpr iter_difference_t<_Ip> operator()(_Ip&& __first, _Sp __last) const {
78 if constexpr (sized_sentinel_for<_Sp, __uncvref_t<_Ip>>) {
79 return __last - __first;
80 } else {
81 return __last - decay_t<_Ip>(__first);
82 }
83 }
84
85 template<range _Rp>
86 _LIBCPP_HIDE_FROM_ABI
operator__fn87 constexpr range_difference_t<_Rp> operator()(_Rp&& __r) const {
88 if constexpr (sized_range<_Rp>) {
89 return static_cast<range_difference_t<_Rp>>(ranges::size(__r));
90 } else {
91 return operator()(ranges::begin(__r), ranges::end(__r));
92 }
93 }
94 };
95
96 } // namespace __distance
97
98 inline namespace __cpo {
99 inline constexpr auto distance = __distance::__fn{};
100 } // namespace __cpo
101 } // namespace ranges
102
103 #endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
104
105 _LIBCPP_END_NAMESPACE_STD
106
107 #endif // _LIBCPP___ITERATOR_DISTANCE_H
108