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_INCREMENTABLE_TRAITS_H 11 #define _LIBCPP___ITERATOR_INCREMENTABLE_TRAITS_H 12 13 #include <__concepts/arithmetic.h> 14 #include <__config> 15 #include <__type_traits/conditional.h> 16 #include <__type_traits/is_object.h> 17 #include <__type_traits/is_primary_template.h> 18 #include <__type_traits/make_signed.h> 19 #include <__type_traits/remove_cvref.h> 20 #include <__utility/declval.h> 21 #include <cstddef> 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 #if _LIBCPP_STD_VER >= 20 30 31 // [incrementable.traits] 32 template <class> 33 struct incrementable_traits {}; 34 35 template <class _Tp> 36 requires is_object_v<_Tp> 37 struct incrementable_traits<_Tp*> { 38 using difference_type = ptrdiff_t; 39 }; 40 41 template <class _Ip> 42 struct incrementable_traits<const _Ip> : incrementable_traits<_Ip> {}; 43 44 template <class _Tp> 45 concept __has_member_difference_type = requires { typename _Tp::difference_type; }; 46 47 template <__has_member_difference_type _Tp> 48 struct incrementable_traits<_Tp> { 49 using difference_type = typename _Tp::difference_type; 50 }; 51 52 template <class _Tp> 53 concept __has_integral_minus = requires(const _Tp& __x, const _Tp& __y) { 54 { __x - __y } -> integral; 55 }; 56 57 template <__has_integral_minus _Tp> 58 requires(!__has_member_difference_type<_Tp>) 59 struct incrementable_traits<_Tp> { 60 using difference_type = make_signed_t<decltype(std::declval<_Tp>() - std::declval<_Tp>())>; 61 }; 62 63 template <class> 64 struct iterator_traits; 65 66 // Let `RI` be `remove_cvref_t<I>`. The type `iter_difference_t<I>` denotes 67 // `incrementable_traits<RI>::difference_type` if `iterator_traits<RI>` names a specialization 68 // generated from the primary template, and `iterator_traits<RI>::difference_type` otherwise. 69 template <class _Ip> 70 using iter_difference_t = 71 typename conditional_t<__is_primary_template<iterator_traits<remove_cvref_t<_Ip> > >::value, 72 incrementable_traits<remove_cvref_t<_Ip> >, 73 iterator_traits<remove_cvref_t<_Ip> > >::difference_type; 74 75 #endif // _LIBCPP_STD_VER >= 20 76 77 _LIBCPP_END_NAMESPACE_STD 78 79 #endif // _LIBCPP___ITERATOR_INCREMENTABLE_TRAITS_H 80