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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-exception7//8//===----------------------------------------------------------------------===//9 10#ifndef _LIBCPP___ITERATOR_INCREMENTABLE_TRAITS_H11#define _LIBCPP___ITERATOR_INCREMENTABLE_TRAITS_H12 13#include <__concepts/arithmetic.h>14#include <__config>15#include <__cstddef/ptrdiff_t.h>16#include <__type_traits/conditional.h>17#include <__type_traits/is_object.h>18#include <__type_traits/is_primary_template.h>19#include <__type_traits/make_signed.h>20#include <__type_traits/remove_cvref.h>21#include <__utility/declval.h>22 23#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)24# pragma GCC system_header25#endif26 27_LIBCPP_BEGIN_NAMESPACE_STD28 29#if _LIBCPP_STD_VER >= 2030 31// [incrementable.traits]32template <class>33struct incrementable_traits {};34 35template <class _Tp>36 requires is_object_v<_Tp>37struct incrementable_traits<_Tp*> {38 using difference_type = ptrdiff_t;39};40 41template <class _Ip>42struct incrementable_traits<const _Ip> : incrementable_traits<_Ip> {};43 44template <class _Tp>45concept __has_member_difference_type = requires { typename _Tp::difference_type; };46 47template <__has_member_difference_type _Tp>48struct incrementable_traits<_Tp> {49 using difference_type = typename _Tp::difference_type;50};51 52template <class _Tp>53concept __has_integral_minus = requires(const _Tp& __x, const _Tp& __y) {54 { __x - __y } -> integral;55};56 57template <__has_integral_minus _Tp>58 requires(!__has_member_difference_type<_Tp>)59struct incrementable_traits<_Tp> {60 using difference_type = make_signed_t<decltype(std::declval<_Tp>() - std::declval<_Tp>())>;61};62 63template <class>64struct iterator_traits;65 66// Let `RI` be `remove_cvref_t<I>`. The type `iter_difference_t<I>` denotes67// `incrementable_traits<RI>::difference_type` if `iterator_traits<RI>` names a specialization68// generated from the primary template, and `iterator_traits<RI>::difference_type` otherwise.69template <class _Ip>70using 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 >= 2076 77_LIBCPP_END_NAMESPACE_STD78 79#endif // _LIBCPP___ITERATOR_INCREMENTABLE_TRAITS_H80