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] 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>` 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. 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 >= 20 76 77_LIBCPP_END_NAMESPACE_STD 78 79#endif // _LIBCPP___ITERATOR_INCREMENTABLE_TRAITS_H 80