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_READABLE_TRAITS_H 11#define _LIBCPP___ITERATOR_READABLE_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// [readable.traits] 29template<class> struct __cond_value_type {}; 30 31template<class _Tp> 32requires is_object_v<_Tp> 33struct __cond_value_type<_Tp> { using value_type = remove_cv_t<_Tp>; }; 34 35template<class _Tp> 36concept __has_member_value_type = requires { typename _Tp::value_type; }; 37 38template<class _Tp> 39concept __has_member_element_type = requires { typename _Tp::element_type; }; 40 41template<class> struct indirectly_readable_traits {}; 42 43template<class _Ip> 44requires is_array_v<_Ip> 45struct indirectly_readable_traits<_Ip> { 46 using value_type = remove_cv_t<remove_extent_t<_Ip>>; 47}; 48 49template<class _Ip> 50struct indirectly_readable_traits<const _Ip> : indirectly_readable_traits<_Ip> {}; 51 52template<class _Tp> 53struct indirectly_readable_traits<_Tp*> : __cond_value_type<_Tp> {}; 54 55template<__has_member_value_type _Tp> 56struct indirectly_readable_traits<_Tp> 57 : __cond_value_type<typename _Tp::value_type> {}; 58 59template<__has_member_element_type _Tp> 60struct indirectly_readable_traits<_Tp> 61 : __cond_value_type<typename _Tp::element_type> {}; 62 63// Pre-emptively applies LWG3541 64template<__has_member_value_type _Tp> 65requires __has_member_element_type<_Tp> 66struct indirectly_readable_traits<_Tp> {}; 67template<__has_member_value_type _Tp> 68requires __has_member_element_type<_Tp> && 69 same_as<remove_cv_t<typename _Tp::element_type>, 70 remove_cv_t<typename _Tp::value_type>> 71struct indirectly_readable_traits<_Tp> 72 : __cond_value_type<typename _Tp::value_type> {}; 73 74template <class> 75struct iterator_traits; 76 77// Let `RI` be `remove_cvref_t<I>`. The type `iter_value_t<I>` denotes 78// `indirectly_readable_traits<RI>::value_type` if `iterator_traits<RI>` names a specialization 79// generated from the primary template, and `iterator_traits<RI>::value_type` otherwise. 80template <class _Ip> 81using iter_value_t = typename conditional_t<__is_primary_template<iterator_traits<remove_cvref_t<_Ip> > >::value, 82 indirectly_readable_traits<remove_cvref_t<_Ip> >, 83 iterator_traits<remove_cvref_t<_Ip> > >::value_type; 84 85#endif // !defined(_LIBCPP_HAS_NO_RANGES) 86 87_LIBCPP_END_NAMESPACE_STD 88 89_LIBCPP_POP_MACROS 90 91#endif // _LIBCPP___ITERATOR_READABLE_TRAITS_H 92