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/decay.h>
21 #include <__type_traits/remove_cvref.h>
22
23 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
24 # pragma GCC system_header
25 #endif
26
27 _LIBCPP_BEGIN_NAMESPACE_STD
28
29 template <class _InputIter>
30 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX17
31 typename iterator_traits<_InputIter>::difference_type
__distance(_InputIter __first,_InputIter __last,input_iterator_tag)32 __distance(_InputIter __first, _InputIter __last, input_iterator_tag)
33 {
34 typename iterator_traits<_InputIter>::difference_type __r(0);
35 for (; __first != __last; ++__first)
36 ++__r;
37 return __r;
38 }
39
40 template <class _RandIter>
41 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX17
42 typename iterator_traits<_RandIter>::difference_type
__distance(_RandIter __first,_RandIter __last,random_access_iterator_tag)43 __distance(_RandIter __first, _RandIter __last, random_access_iterator_tag)
44 {
45 return __last - __first;
46 }
47
48 template <class _InputIter>
49 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX17
50 typename iterator_traits<_InputIter>::difference_type
distance(_InputIter __first,_InputIter __last)51 distance(_InputIter __first, _InputIter __last)
52 {
53 return _VSTD::__distance(__first, __last, typename iterator_traits<_InputIter>::iterator_category());
54 }
55
56 #if _LIBCPP_STD_VER > 17
57
58 // [range.iter.op.distance]
59
60 namespace ranges {
61 namespace __distance {
62
63 struct __fn {
64 template<class _Ip, sentinel_for<_Ip> _Sp>
65 requires (!sized_sentinel_for<_Sp, _Ip>)
66 _LIBCPP_HIDE_FROM_ABI
operator__fn67 constexpr iter_difference_t<_Ip> operator()(_Ip __first, _Sp __last) const {
68 iter_difference_t<_Ip> __n = 0;
69 while (__first != __last) {
70 ++__first;
71 ++__n;
72 }
73 return __n;
74 }
75
76 template<class _Ip, sized_sentinel_for<decay_t<_Ip>> _Sp>
77 _LIBCPP_HIDE_FROM_ABI
operator__fn78 constexpr iter_difference_t<_Ip> operator()(_Ip&& __first, _Sp __last) const {
79 if constexpr (sized_sentinel_for<_Sp, __remove_cvref_t<_Ip>>) {
80 return __last - __first;
81 } else {
82 return __last - decay_t<_Ip>(__first);
83 }
84 }
85
86 template<range _Rp>
87 _LIBCPP_HIDE_FROM_ABI
operator__fn88 constexpr range_difference_t<_Rp> operator()(_Rp&& __r) const {
89 if constexpr (sized_range<_Rp>) {
90 return static_cast<range_difference_t<_Rp>>(ranges::size(__r));
91 } else {
92 return operator()(ranges::begin(__r), ranges::end(__r));
93 }
94 }
95 };
96
97 } // namespace __distance
98
99 inline namespace __cpo {
100 inline constexpr auto distance = __distance::__fn{};
101 } // namespace __cpo
102 } // namespace ranges
103
104 #endif // _LIBCPP_STD_VER > 17
105
106 _LIBCPP_END_NAMESPACE_STD
107
108 #endif // _LIBCPP___ITERATOR_DISTANCE_H
109