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 <__config> 14#include <concepts> 15#include <type_traits> 16 17#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 18#pragma GCC system_header 19#endif 20 21_LIBCPP_PUSH_MACROS 22#include <__undef_macros> 23 24_LIBCPP_BEGIN_NAMESPACE_STD 25 26#if !defined(_LIBCPP_HAS_NO_RANGES) 27 28// [incrementable.traits] 29template<class> struct incrementable_traits {}; 30 31template<class _Tp> 32requires is_object_v<_Tp> 33struct incrementable_traits<_Tp*> { 34 using difference_type = ptrdiff_t; 35}; 36 37template<class _Ip> 38struct incrementable_traits<const _Ip> : incrementable_traits<_Ip> {}; 39 40template<class _Tp> 41concept __has_member_difference_type = requires { typename _Tp::difference_type; }; 42 43template<__has_member_difference_type _Tp> 44struct incrementable_traits<_Tp> { 45 using difference_type = typename _Tp::difference_type; 46}; 47 48template<class _Tp> 49concept __has_integral_minus = 50 requires(const _Tp& __x, const _Tp& __y) { 51 { __x - __y } -> integral; 52 }; 53 54template<__has_integral_minus _Tp> 55requires (!__has_member_difference_type<_Tp>) 56struct incrementable_traits<_Tp> { 57 using difference_type = make_signed_t<decltype(declval<_Tp>() - declval<_Tp>())>; 58}; 59 60template <class> 61struct iterator_traits; 62 63// Let `RI` be `remove_cvref_t<I>`. The type `iter_difference_t<I>` denotes 64// `incrementable_traits<RI>::difference_type` if `iterator_traits<RI>` names a specialization 65// generated from the primary template, and `iterator_traits<RI>::difference_type` otherwise. 66template <class _Ip> 67using iter_difference_t = typename conditional_t<__is_primary_template<iterator_traits<remove_cvref_t<_Ip> > >::value, 68 incrementable_traits<remove_cvref_t<_Ip> >, 69 iterator_traits<remove_cvref_t<_Ip> > >::difference_type; 70 71#endif // !defined(_LIBCPP_HAS_NO_RANGES) 72 73_LIBCPP_END_NAMESPACE_STD 74 75_LIBCPP_POP_MACROS 76 77#endif // _LIBCPP___ITERATOR_INCREMENTABLE_TRAITS_H 78