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] 29 template<class> struct __cond_value_type {}; 30 31 template<class _Tp> 32 requires is_object_v<_Tp> 33 struct __cond_value_type<_Tp> { using value_type = remove_cv_t<_Tp>; }; 34 35 template<class _Tp> 36 concept __has_member_value_type = requires { typename _Tp::value_type; }; 37 38 template<class _Tp> 39 concept __has_member_element_type = requires { typename _Tp::element_type; }; 40 41 template<class> struct indirectly_readable_traits {}; 42 43 template<class _Ip> 44 requires is_array_v<_Ip> 45 struct indirectly_readable_traits<_Ip> { 46 using value_type = remove_cv_t<remove_extent_t<_Ip>>; 47 }; 48 49 template<class _Ip> 50 struct indirectly_readable_traits<const _Ip> : indirectly_readable_traits<_Ip> {}; 51 52 template<class _Tp> 53 struct indirectly_readable_traits<_Tp*> : __cond_value_type<_Tp> {}; 54 55 template<__has_member_value_type _Tp> 56 struct indirectly_readable_traits<_Tp> 57 : __cond_value_type<typename _Tp::value_type> {}; 58 59 template<__has_member_element_type _Tp> 60 struct indirectly_readable_traits<_Tp> 61 : __cond_value_type<typename _Tp::element_type> {}; 62 63 // Pre-emptively applies LWG3541 64 template<__has_member_value_type _Tp> 65 requires __has_member_element_type<_Tp> 66 struct indirectly_readable_traits<_Tp> {}; 67 template<__has_member_value_type _Tp> 68 requires __has_member_element_type<_Tp> && 69 same_as<remove_cv_t<typename _Tp::element_type>, 70 remove_cv_t<typename _Tp::value_type>> 71 struct indirectly_readable_traits<_Tp> 72 : __cond_value_type<typename _Tp::value_type> {}; 73 74 template <class> 75 struct 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. 80 template <class _Ip> 81 using 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