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_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 typename iterator_traits<_InputIter>::difference_type 31 __distance(_InputIter __first, _InputIter __last, input_iterator_tag) { 32 typename iterator_traits<_InputIter>::difference_type __r(0); 33 for (; __first != __last; ++__first) 34 ++__r; 35 return __r; 36 } 37 38 template <class _RandIter> 39 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 typename iterator_traits<_RandIter>::difference_type 40 __distance(_RandIter __first, _RandIter __last, random_access_iterator_tag) { 41 return __last - __first; 42 } 43 44 template <class _InputIter> 45 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 typename iterator_traits<_InputIter>::difference_type 46 distance(_InputIter __first, _InputIter __last) { 47 return std::__distance(__first, __last, typename iterator_traits<_InputIter>::iterator_category()); 48 } 49 50 #if _LIBCPP_STD_VER >= 20 51 52 // [range.iter.op.distance] 53 54 namespace ranges { 55 struct __distance { 56 template <class _Ip, sentinel_for<_Ip> _Sp> 57 requires(!sized_sentinel_for<_Sp, _Ip>) 58 _LIBCPP_HIDE_FROM_ABI constexpr iter_difference_t<_Ip> operator()(_Ip __first, _Sp __last) const { 59 iter_difference_t<_Ip> __n = 0; 60 while (__first != __last) { 61 ++__first; 62 ++__n; 63 } 64 return __n; 65 } 66 67 template <class _Ip, sized_sentinel_for<decay_t<_Ip>> _Sp> 68 _LIBCPP_HIDE_FROM_ABI constexpr iter_difference_t<_Ip> operator()(_Ip&& __first, _Sp __last) const { 69 if constexpr (sized_sentinel_for<_Sp, __remove_cvref_t<_Ip>>) { 70 return __last - __first; 71 } else { 72 return __last - decay_t<_Ip>(__first); 73 } 74 } 75 76 template <range _Rp> 77 _LIBCPP_HIDE_FROM_ABI constexpr range_difference_t<_Rp> operator()(_Rp&& __r) const { 78 if constexpr (sized_range<_Rp>) { 79 return static_cast<range_difference_t<_Rp>>(ranges::size(__r)); 80 } else { 81 return operator()(ranges::begin(__r), ranges::end(__r)); 82 } 83 } 84 }; 85 86 inline namespace __cpo { 87 inline constexpr auto distance = __distance{}; 88 } // namespace __cpo 89 } // namespace ranges 90 91 #endif // _LIBCPP_STD_VER >= 20 92 93 _LIBCPP_END_NAMESPACE_STD 94 95 #endif // _LIBCPP___ITERATOR_DISTANCE_H 96